153-715: The National Recording Registry is a list of sound recordings that "are culturally, historically, or aesthetically significant, and inform or reflect life in the United States ." The registry was established by the National Recording Preservation Act of 2000, which created the National Recording Preservation Board , whose members are appointed by the Librarian of Congress . The recordings preserved in
306-398: A Stroh violin which uses a conical horn connected to a diaphragm that in turn is connected to the violin bridge. The horn was no longer needed once electrical recording was developed. The long-playing 33 1 ⁄ 3 rpm microgroove LP record , was developed at Columbia Records and introduced in 1948. The short-playing but convenient 7-inch (18 cm) 45 rpm microgroove vinyl single
459-455: A conductor 's surface, since otherwise there would be a force along the surface of the conductor that would move the charge carriers to even the potential across the surface. The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre,
612-461: A force on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended by a fine thread can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball
765-512: A microphone was used to convert the sound into an electrical signal that was amplified and used to actuate the recording stylus. This innovation eliminated the "horn sound" resonances characteristic of the acoustical process, produced clearer and more full-bodied recordings by greatly extending the useful range of audio frequencies, and allowed previously unrecordable distant and feeble sounds to be captured. During this time, several radio-related developments in electronics converged to revolutionize
918-685: A sound track . The projector used a steady light and a photodetector to convert these variations back into an electrical signal, which was amplified and sent to loudspeakers behind the screen. Optical sound became the standard motion picture audio system throughout the world and remains so for theatrical release prints despite attempts in the 1950s to substitute magnetic soundtracks. Currently, all release prints on 35 mm movie film include an analog optical soundtrack, usually stereo with Dolby SR noise reduction. In addition, an optically recorded digital soundtrack in Dolby Digital or Sony SDDS form
1071-409: A steady state current, but instead blocks it. The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality
1224-469: A Brahms Serenade, and the last movement of Bruckner's 8th Symphony with Von Karajan. Other early German stereophonic tapes are believed to have been destroyed in bombings. Not until Ampex introduced the first commercial two-track tape recorders in the late 1940s did stereo tape recording become commercially feasible. Despite the availability of multitrack tape, stereo did not become the standard system for commercial music recording for some years, and remained
1377-456: A central role in many modern technologies, serving in electric power where electric current is used to energise equipment, and in electronics dealing with electrical circuits involving active components such as vacuum tubes , transistors , diodes and integrated circuits , and associated passive interconnection technologies. The study of electrical phenomena dates back to antiquity, with theoretical understanding progressing slowly until
1530-432: A charge of Q coulombs every t seconds passing through an electric potential ( voltage ) difference of V is where Electric power is generally supplied to businesses and homes by the electric power industry . Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters , which keep
1683-407: A coating of soot as the paper was passed under it. An 1860 phonautogram of " Au Clair de la Lune ", a French folk song, was played back as sound for the first time in 2008 by scanning it and using software to convert the undulating line, which graphically encoded the sound, into a corresponding digital audio file. Thomas Edison's work on two other innovations, the telegraph and the telephone, led to
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#17327730193031836-516: A common reference point to which potentials may be expressed and compared is useful. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground . Earth is assumed to be an infinite source of equal amounts of positive and negative charge and is therefore electrically uncharged—and unchargeable. Electric potential
1989-485: A condenser type developed there in 1916 and greatly improved in 1922, and the best amplifiers and test equipment. They had already patented an electromechanical recorder in 1918, and in the early 1920s, they decided to intensively apply their hardware and expertise to developing two state-of-the-art systems for electronically recording and reproducing sound: one that employed conventional discs and another that recorded optically on motion picture film. Their engineers pioneered
2142-472: A current of one amp. The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance . The unit of capacitance
2295-494: A dampened kite string and flown the kite in a storm-threatened sky . A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1775, Hugh Williamson reported
2448-402: A few crude telephone-based recording devices with no means of amplification, such as the telegraphone , it remained so until the 1920s. Between the invention of the phonograph in 1877 and the first commercial digital recordings in the early 1970s, arguably the most important milestone in the history of sound recording was the introduction of what was then called electrical recording , in which
2601-556: A fund-raising foundation. The purpose of the Registry is to maintain and preserve sound recordings and collections of sound recordings that are culturally, historically, or aesthetically significant. Beginning in 2002, the National Recording Preservation Board has selected recordings nominated each year to be preserved. On January 27, 2003, the first 50 recordings were announced by James Billington ,
2754-509: A high level of complexity and sophistication. The combined impact with innovations such as the endless loop broadcast cartridge led to significant changes in the pacing and production style of radio program content and advertising. In 1881, it was noted during experiments in transmitting sound from the Paris Opera that it was possible to follow the movement of singers on the stage if earpieces connected to different microphones were held to
2907-425: A large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor , the sharp spike of which acts to encourage the lightning strike to develop there, rather than to
3060-585: A major consumer audio format and advances in electronic and mechanical miniaturization led to the development of the Sony Walkman , a pocket-sized cassette player introduced in 1979. The Walkman was the first personal music player and it gave a major boost to sales of prerecorded cassettes. A key advance in audio fidelity came with the Dolby A noise reduction system, invented by Ray Dolby and introduced into professional recording studios in 1966. It suppressed
3213-743: A master roll which had been created on a special piano, which punched holes in the master as a live performer played the song. Thus, the roll represented a recording of the actual performance of an individual, not just the more common method of punching the master roll through transcription of the sheet music. This technology to record a live performance onto a piano roll was not developed until 1904. Piano rolls were in continuous mass production from 1896 to 2008. A 1908 U.S. Supreme Court copyright case noted that, in 1902 alone, there were between 70,000 and 75,000 player pianos manufactured, and between 1,000,000 and 1,500,000 piano rolls produced. The first device that could record actual sounds as they passed through
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#17327730193033366-402: A millimetre per second, the electric field that drives them itself propagates at close to the speed of light , enabling electrical signals to pass rapidly along wires. Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800,
3519-553: A more reliable source of electrical energy than the electrostatic machines previously used. The recognition of electromagnetism , the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–1820. Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827. Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell , in particular in his " On Physical Lines of Force " in 1861 and 1862. While
3672-554: A much larger proportion of people to hear famous orchestras, operas, singers and bands, because even if a person could not afford to hear the live concert, they may be able to hear the recording. The availability of sound recording thus helped to spread musical styles to new regions, countries and continents. The cultural influence went in a number of directions. Sound recordings enabled Western music lovers to hear actual recordings of Asian, Middle Eastern and African groups and performers, increasing awareness of non-Western musical styles. At
3825-425: A positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current . The motion of negatively charged electrons around an electric circuit , one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of
3978-420: A positive or negative electric charge produces an electric field . The motion of electric charges is an electric current and produces a magnetic field . In most applications, Coulomb's law determines the force acting on an electric charge. Electric potential is the work done to move an electric charge from one point to another within an electric field, typically measured in volts . Electricity plays
4131-891: A practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work. An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task. The components in an electric circuit can take many forms, which can include elements such as resistors , capacitors , switches , transformers and electronics . Electronic circuits contain active components , usually semiconductors , and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear : while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli. The resistor
4284-406: A process now known as electrolysis . Their work was greatly expanded upon by Michael Faraday in 1833. Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in
4437-471: A rapidly changing one. Electric power is the rate at which electric energy is transferred by an electric circuit . The SI unit of power is the watt , one joule per second . Electric power, like mechanical power , is the rate of doing work , measured in watts , and represented by the letter P . The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of
4590-489: A resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm , the unit of resistance, was named in honour of Georg Ohm , and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to
4743-402: A result, each performance of a song or piece would be slightly different. With the development of analog sound recording, though, a performance could be permanently fixed, in all of its elements: pitch, rhythm, timbre, ornaments and expression. This meant that many more elements of a performance would be captured and disseminated to other listeners. The development of sound recording also enabled
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4896-600: A revival of vinyl in the music industry, as well as analog electronics, and analog type plug-ins for recording and mixing software. Electrical Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge . Electricity is related to magnetism , both being part of the phenomenon of electromagnetism , as described by Maxwell's equations . Common phenomena are related to electricity, including lightning , static electricity , electric heating , electric discharges and many others. The presence of either
5049-595: A running total of the electric energy delivered to a customer. Unlike fossil fuels , electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes , transistors , diodes , sensors and integrated circuits , and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes digital switching possible, and electronics
5202-431: A scientific curiosity into an essential tool for modern life. In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to
5355-575: A series of experiments to the Royal Society on the shocks delivered by the electric eel ; that same year the surgeon and anatomist John Hunter described the structure of the fish's electric organs . In 1791, Luigi Galvani published his discovery of bioelectromagnetics , demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta 's battery, or voltaic pile , of 1800, made from alternating layers of zinc and copper, provided scientists with
5508-515: A series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic , in contrast to minerals such as magnetite , which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating , based on
5661-477: A solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect. In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flow can be understood in two forms: as negatively charged electrons , and as positively charged electron deficiencies called holes . These charges and holes are understood in terms of quantum physics. The building material
5814-510: A specialist market during the 1950s. EMI (UK) was the first company to release commercial stereophonic tapes. They issued their first Stereosonic tape in 1954. Others quickly followed, under the His Master's Voice (HMV) and Columbia labels. 161 Stereosonic tapes were released, mostly classical music or lyric recordings. RCA imported these tapes into the USA. Although some HMV tapes released in
5967-464: A stereo soundtrack was Walt Disney's Fantasia , released in 1940. The 1941 release of Fantasia used the Fantasound sound system. This system used a separate film for the sound, synchronized with the film carrying the picture. The sound film had four double-width optical soundtracks, three for left, center, and right audio—and a fourth as a "control" track with three recorded tones that controlled
6120-469: A variety of materials including mild steel, thorn, and even sapphire. Discs had a distinctly limited playing life that varied depending on how they were manufactured. Earlier, purely acoustic methods of recording had limited sensitivity and frequency range. Mid-frequency range notes could be recorded, but very low and very high frequencies could not. Instruments such as the violin were difficult to transfer to disc. One technique to deal with this involved using
6273-429: A variety of techniques from remixing to pseudostereo . Magnetic tape transformed the recording industry. By the early 1950s, most commercial recordings were mastered on tape instead of recorded directly to disc. Tape facilitated a degree of manipulation in the recording process that was impractical with mixes and multiple generations of directly recorded discs. An early example is Les Paul 's 1951 recording of How High
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6426-476: A wide frequency range and high audio quality are not. The development of analog sound recording in the nineteenth century and its widespread use throughout the twentieth century had a huge impact on the development of music. Before analog sound recording was invented, most music was as a live performance. Throughout the medieval , Renaissance , Baroque , Classical , and through much of the Romantic music era ,
6579-511: A wire disturbing the needle of a magnetic compass. He had discovered electromagnetism , a fundamental interaction between electricity and magnetics. The level of electromagnetic emissions generated by electric arcing is high enough to produce electromagnetic interference , which can be detrimental to the workings of adjacent equipment. In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how
6732-448: A wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained. Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction , enabled him to state
6885-402: A wire. The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other. Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope , which although still in use for classroom demonstrations, has been superseded by
7038-550: A worldwide standard for higher-quality recording on vinyl records. The Ernest Ansermet recording of Igor Stravinsky 's Petrushka was key in the development of full frequency range records and alerting the listening public to high fidelity in 1946. Until the mid-1960s, record companies mixed and released most popular music in monophonic sound. From mid-1960s until the early 1970s, major recordings were commonly released in both mono and stereo. Recordings originally released only in mono have been rerendered and released in stereo using
7191-474: Is amplified and connected to a loudspeaker to produce sound. Long before sound was first recorded, music was recorded—first by written music notation , then also by mechanical devices (e.g., wind-up music boxes , in which a mechanism turns a spindle, which plucks metal tines, thus reproducing a melody ). Automatic music reproduction traces back as far as the 9th century, when the Banū Mūsā brothers invented
7344-584: Is a scalar quantity . That is, it has only magnitude and not direction. It may be viewed as analogous to height : just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field. As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials ) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to
7497-411: Is a vector field . The study of electric fields created by stationary charges is called electrostatics . The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term ' lines of force ' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it
7650-411: Is achieved by a microphone diaphragm that senses changes in atmospheric pressure caused by acoustic sound waves and records them as a mechanical representation of the sound waves on a medium such as a phonograph record (in which a stylus cuts grooves on a record). In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current , which
7803-452: Is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker. An electric field generally varies in space, and its strength at any one point
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#17327730193037956-401: Is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb , who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract . The force acts on
8109-473: Is defined as negative, and that by protons is positive. Before these particles were discovered, Benjamin Franklin had defined a positive charge as being the charge acquired by a glass rod when it is rubbed with a silk cloth. A proton by definition carries a charge of exactly 1.602 176 634 × 10 coulombs . This value is also defined as the elementary charge . No object can have a charge smaller than
8262-483: Is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point. The conceptual charge, termed a ' test charge ', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields . As the electric field is defined in terms of force , and force is a vector , having both magnitude and direction , it follows that an electric field
8415-531: Is integral to applications spanning transport , heating , lighting , communications , and computation , making it the foundation of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish . Ancient Egyptian texts dating from 2750 BCE described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek , Roman and Arabic naturalists and physicians . Several ancient writers, such as Pliny
8568-417: Is likely to be present. An optically recorded timecode is also commonly included to synchronize CDROMs that contain a DTS soundtrack. This period also saw several other historic developments including the introduction of the first practical magnetic sound recording system, the magnetic wire recorder , which was based on the work of Danish inventor Valdemar Poulsen . Magnetic wire recorders were effective, but
8721-406: Is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere . This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury . A current was allowed through
8874-415: Is most often a crystalline semiconductor . Solid-state electronics came into its own with the emergence of transistor technology. The first working transistor, a germanium -based point-contact transistor , was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947, followed by the bipolar junction transistor in 1948. By modern convention, the charge carried by electrons
9027-403: Is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory , stating that the current passing through
9180-531: Is subjected to transients , such as when first energised. The concept of the electric field was introduced by Michael Faraday . An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses , and like it, extends towards infinity and shows an inverse square relationship with distance. However, there
9333-406: Is termed the inductance . The unit of inductance is the henry , named after Joseph Henry , a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes
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#17327730193039486-415: Is the farad , named after Michael Faraday , and given the symbol F : one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit
9639-446: Is the first piece of video game music to be selected for the Registry. Sound recording Sound recording and reproduction is the electrical , mechanical , electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music , or sound effects . The two main classes of sound recording technology are analog recording and digital recording . Acoustic analog recording
9792-422: Is then converted to a varying magnetic field by an electromagnet , which makes a representation of the sound as magnetized areas on a plastic tape with a magnetic coating on it. Analog sound reproduction is the reverse process, with a larger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Digital recording and reproduction converts the analog sound signal picked up by
9945-529: Is therefore 0 at all places inside the body. This is the operating principal of the Faraday cage , a conducting metal shell which isolates its interior from outside electrical effects. The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between
10098-409: Is usually measured in volts , and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference , and is the energy required to move a unit charge between two specified points. An electric field has
10251-536: Is widely used in information processing , telecommunications , and signal processing . Interconnection technologies such as circuit boards , electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system . Today, most electronic devices use semiconductor components to perform electron control. The underlying principles that explain how semiconductors work are studied in solid state physics , whereas
10404-568: The Chladni patterns produced by sound in stone representations, although this theory has not been conclusively proved. In the 14th century, a mechanical bell-ringer controlled by a rotating cylinder was introduced in Flanders . Similar designs appeared in barrel organs (15th century), musical clocks (1598), barrel pianos (1805), and music boxes ( c. 1800 ). A music box is an automatic musical instrument that produces sounds by
10557-621: The King James Bible is over 80 hours, and Lyndon B. Johnson 's recordings are nearly 850 hours in length. Two significant podcast episodes are included: " The Giant Pool of Money " from This American Life (focusing on the subprime mortgage crisis causing the Great Recession ) and the Robin Williams interview from WTF with Marc Maron (before his death from suicide in 2014). The Super Mario Bros. theme
10710-413: The Librarian of Congress . The first four yearly lists each had 50 selections. Since 2006, 25 recordings have been selected annually. As of 2024, a total of 650 recordings have been preserved in the Registry. Each calendar year, public nominations are accepted for inclusion in that year's list of selections, which are announced the following spring. Registry title works, original or copies, are housed at
10863-721: The Neo-Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron , the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne 's Pseudodoxia Epidemica of 1646. Isaac Newton made early investigations into electricity, with an idea of his written down in his book Opticks arguably
11016-536: The compact disc (CD) in 1982 brought significant improvements in the quality and durability of recordings. The CD initiated another massive wave of change in the consumer music industry, with vinyl records effectively relegated to a small niche market by the mid-1990s. The record industry fiercely resisted the introduction of digital systems, fearing wholesale piracy on a medium able to produce perfect copies of original released recordings. The most recent and revolutionary developments have been in digital recording, with
11169-423: The electromagnetic force , one of the four fundamental forces of nature. Experiment has shown charge to be a conserved quantity , that is, the net charge within an electrically isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as
11322-452: The graphic equalizer , which could be connected together to create a complete home sound system. These developments were rapidly taken up by major Japanese electronics companies, which soon flooded the world market with relatively affordable, high-quality transistorized audio components. By the 1980s, corporations like Sony had become world leaders in the music recording and playback industry. The advent of digital sound recording and later
11475-522: The quantum revolution. Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect". The photoelectric effect is also employed in photocells such as can be found in solar panels . The first solid-state device was the " cat's-whisker detector " first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with
11628-452: The strong interaction , but unlike that force it operates over all distances. In comparison with the much weaker gravitational force , the electromagnetic force pushing two electrons apart is 10 times that of the gravitational attraction pulling them together. Charge originates from certain types of subatomic particles , the most familiar carriers of which are the electron and proton . Electric charge gives rise to and interacts with
11781-541: The 17th and 18th centuries. The development of the theory of electromagnetism in the 19th century marked significant progress, leading to electricity's industrial and residential application by electrical engineers by the century's end. This rapid expansion in electrical technology at the time was the driving force behind the Second Industrial Revolution , with electricity's versatility driving transformations in both industry and society. Electricity
11934-406: The 1920s, Phonofilm and other early motion picture sound systems employed optical recording technology, in which the audio signal was graphically recorded on photographic film. The amplitude variations comprising the signal were used to modulate a light source which was imaged onto the moving film through a narrow slit, allowing the signal to be photographed as variations in the density or width of
12087-545: The 1936 discovery of the Baghdad Battery , which resembles a galvanic cell , though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete , in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined
12240-549: The 1980s, but in the 1960s the pre-recorded 8-track tape was launched as a consumer audio format by the Lear Jet aircraft company. Aimed particularly at the automotive market, they were the first practical, affordable car hi-fi systems, and could produce sound quality superior to that of the compact cassette. The smaller size and greater durability – augmented by the ability to create home-recorded music mixtapes since 8-track recorders were rare – saw
12393-656: The Elder and Scribonius Largus , attested to the numbing effect of electric shocks delivered by electric catfish and electric rays , and knew that such shocks could travel along conducting objects. Patients with ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber , could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made
12546-738: The Library of Congress' Packard Campus for Audio Video Conservation . Each yearly list typically includes a few recordings that have also been selected for inclusion in the holdings of the National Archives ' audiovisual collection. Recordings on the National Recording Registry that are of a political nature tend to overlap with the audiovisual collection of the National Archives. The criteria for selection are: The list shows overlapping items and whether
12699-483: The Moon , on which Paul played eight overdubbed guitar tracks. In the 1960s Brian Wilson of The Beach Boys , Frank Zappa , and The Beatles (with producer George Martin ) were among the first popular artists to explore the possibilities of multitrack recording techniques and effects on their landmark albums Pet Sounds , Freak Out! , and Sgt. Pepper's Lonely Hearts Club Band . The next important innovation
12852-486: The National Archives has an original or a copy of the recording. As of 2023, the oldest recording on the list is Edouard-Leon Scott de Martinville 's Phonautograms which date back to the 1850s. The most recent is the Chamber Music Northwest 's rendition of Ellen Taaffe Zwilich 's Concerto for Clarinet and Chamber Ensemble from 2012. Selections vary widely in duration. The early Edison recordings,
13005-597: The USA cost up to $ 15, two-track stereophonic tapes were more successful in America during the second half of the 1950s. The history of stereo recording changed after the late 1957 introduction of the Westrex stereo phonograph disc , which used the groove format developed earlier by Blumlein. Decca Records in England came out with FFRR (Full Frequency Range Recording) in the 1940s, which became internationally accepted as
13158-560: The United States National Recording Registry form a registry of recordings selected yearly by the National Recording Preservation Board for preservation in the Library of Congress . The National Recording Preservation Act of 2000 established a national program to guard America's sound recording heritage. The Act created the National Recording Registry, The National Recording Preservation Board and
13311-500: The additional benefit of being marginally louder than cylinders. Sales of the gramophone record overtook the cylinder ca. 1910, and by the end of World War I the disc had become the dominant commercial recording format. Edison, who was the main producer of cylinders, created the Edison Disc Record in an attempt to regain his market. The double-sided (nominally 78 rpm) shellac disc was the standard consumer music format from
13464-407: The air (but could not play them back—the purpose was only visual study) was the phonautograph , patented in 1857 by Parisian inventor Édouard-Léon Scott de Martinville . The earliest known recordings of the human voice are phonautograph recordings, called phonautograms , made in 1857. They consist of sheets of paper with sound-wave-modulated white lines created by a vibrating stylus that cut through
13617-494: The amount of data that can be stored on a single medium, such as Super Audio CD , DVD-A , Blu-ray Disc , and HD DVD became available, longer programs of higher quality fit onto a single disc. Sound files are readily downloaded from the Internet and other sources, and copied onto computers and digital audio players. Digital audio technology is now used in all areas of audio, from casual use of music files of moderate quality to
13770-417: The background of hiss, which was the only easily audible downside of mastering on tape instead of recording directly to disc. A competing system, dbx , invented by David Blackmer, also found success in professional audio. A simpler variant of Dolby's noise reduction system, known as Dolby B, greatly improved the sound of cassette tape recordings by reducing the especially high level of hiss that resulted from
13923-555: The basis of all electronic sound systems until the commercial introduction of the first transistor -based audio devices in the mid-1950s. During World War I, engineers in the United States and Great Britain worked on ways to record and reproduce, among other things, the sound of a German U-boat for training purposes. Acoustical recording methods of the time could not reproduce the sounds accurately. The earliest results were not promising. The first electrical recording issued to
14076-408: The beginning of the field theory of the electric force. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke , Robert Boyle , Stephen Gray and C. F. du Fay . Later in the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of
14229-419: The building it serves to protect. The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work . The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It
14382-454: The cassette become the dominant consumer format for portable audio devices in the 1970s and 1980s. There had been experiments with multi-channel sound for many years – usually for special musical or cultural events – but the first commercial application of the concept came in the early 1970s with the introduction of Quadraphonic sound. This spin-off development from multitrack recording used four tracks (instead of
14535-407: The cassette's miniaturized tape format. The compact cassette format also benefited from improvements to the tape itself as coatings with wider frequency responses and lower inherent noise were developed, often based on cobalt and chrome oxides as the magnetic material instead of the more usual iron oxide. The multitrack audio cartridge had been in wide use in the radio industry, from the late 1950s to
14688-426: The charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law , which relates the force to the product of the charges and has an inverse-square relation to the distance between them. The electromagnetic force is very strong, second only in strength to
14841-450: The charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre. The most visible natural occurrence of this is lightning , caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of
14994-447: The commercial recording, distribution, and sale of sound recordings became a growing new international industry, with the most popular titles selling millions of units by the early 1900s. A process for mass-producing duplicate wax cylinders by molding instead of engraving them was put into effect in 1901. The development of mass-production techniques enabled cylinder recordings to become a major new consumer item in industrial countries and
15147-505: The controversy came to focus on concern for the perception of moving image and sound. There are individual and cultural preferences for either method. While approaches and opinions vary, some emphasize sound as paramount, others focus on technology preferences as the deciding factor. Analog fans might embrace limitations as strengths of the medium inherent in the compositional, editing, mixing, and listening phases. Digital advocates boast flexibility in similar processes. This debate fosters
15300-456: The correct equipment, of the released music. It eventually faded out in the late 1970s, although this early venture paved the way for the eventual introduction of domestic surround sound systems in home theatre use, which gained popularity following the introduction of the DVD. The replacement of the relatively fragile vacuum tube by the smaller, rugged and efficient transistor also accelerated
15453-538: The cumbersome disc-to-disc editing procedures previously in some limited use, together with tape's consistently high audio quality finally convinced radio networks to routinely prerecord their entertainment programming, most of which had formerly been broadcast live. Also, for the first time, broadcasters, regulators and other interested parties were able to undertake comprehensive audio logging of each day's radio broadcasts. Innovations like multitracking and tape echo allowed radio programs and advertisements to be produced to
15606-411: The current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes
15759-407: The cylinder was the main consumer format from the late 1880s until around 1910. The next major technical development was the invention of the gramophone record , generally credited to Emile Berliner and patented in 1887, though others had demonstrated similar disk apparatus earlier, most notably Alexander Graham Bell in 1881. Discs were easier to manufacture, transport and store, and they had
15912-516: The design and construction of electronic circuits to solve practical problems are part of electronics engineering . Faraday's and Ampère's work showed that a time-varying magnetic field created an electric field, and a time-varying electric field created a magnetic field. Thus, when either field is changing in time, a field of the other is always induced. These variations are an electromagnetic wave . Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed
16065-572: The development of the phonograph. Edison was working on a machine in 1877 that would transcribe telegraphic signals onto paper tape, which could then be transferred over the telegraph again and again. The phonograph was both in a cylinder and a disc form. On April 30, 1877, French poet, humorous writer and inventor Charles Cros submitted a sealed envelope containing a letter to the Academy of Sciences in Paris fully explaining his proposed method, called
16218-490: The development of various uncompressed and compressed digital audio file formats , processors capable and fast enough to convert the digital data to sound in real time , and inexpensive mass storage . This generated new types of portable digital audio players . The minidisc player, using ATRAC compression on small, re-writeable discs was introduced in the 1990s, but became obsolescent as solid-state non-volatile flash memory dropped in price. As technologies that increase
16371-507: The earliest known mechanical musical instrument, in this case, a hydropowered (water-powered) organ that played interchangeable cylinders. According to Charles B. Fowler, this "... cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century." Carvings in the Rosslyn Chapel from the 1560s may represent an early attempt to record
16524-444: The early 1910s to the late 1950s. In various permutations, the audio disc format became the primary medium for consumer sound recordings until the end of the 20th century. Although there was no universally accepted speed, and various companies offered discs that played at several different speeds, the major recording companies eventually settled on a de facto industry standard of nominally 78 revolutions per minute. The specified speed
16677-478: The early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering . Through such people as Alexander Graham Bell , Ottó Bláthy , Thomas Edison , Galileo Ferraris , Oliver Heaviside , Ányos Jedlik , William Thomson, 1st Baron Kelvin , Charles Algernon Parsons , Werner von Siemens , Joseph Swan , Reginald Fessenden , Nikola Tesla and George Westinghouse , electricity turned from
16830-427: The effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère , who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart. The interaction
16983-448: The electronic electrometer . The movement of electric charge is known as an electric current , the intensity of which is usually measured in amperes . Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. Electric current can flow through some things, electrical conductors , but will not flow through an electrical insulator . By historical convention,
17136-416: The electrons. However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. The process by which electric current passes through a material is termed electrical conduction , and its nature varies with that of the charged particles and
17289-428: The elementary charge, and any amount of charge an object may carry is a multiple of the elementary charge. An electron has an equal negative charge, i.e. −1.602 176 634 × 10 coulombs . Charge is possessed not just by matter , but also by antimatter , each antiparticle bearing an equal and opposite charge to its corresponding particle. The presence of charge gives rise to an electrostatic force: charges exert
17442-495: The form of a sine wave . Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance . These properties however can become important when circuitry
17595-402: The high recording speeds required, they used enormous reels about one meter in diameter, and the thin tape frequently broke, sending jagged lengths of razor steel flying around the studio. Magnetic tape recording uses an amplified electrical audio signal to generate analogous variations of the magnetic field produced by a tape head , which impresses corresponding variations of magnetization on
17748-585: The instrumental " Rumble " by Link Wray , " Rock Around the Clock " by Bill Haley and His Comets and the Super Mario Bros. theme by Koji Kondo each clock in at under three minutes. The Edison "Talking Doll" cylinder is only 17 seconds long and some of Scott de Martinville's Phonautographs are just as brief. Meanwhile, Georg Solti 's recording of Wagner 's complete Ring Cycle is approximately 15 hours in duration, Alexander Scourby 's recitation of
17901-540: The main way that songs and instrumental pieces were recorded was through music notation . While notation indicates the pitches of the melody and their rhythm many aspects of the performance are undocumented. Indeed, in the Medieval era, Gregorian chant did not indicate the rhythm of the chant. In the Baroque era, instrumental pieces often lack a tempo indication and usually none of the ornaments were written down. As
18054-400: The material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis , where ions (charged atoms ) flow through liquids, or through plasmas such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of
18207-475: The microphone to a digital form by the process of sampling . This lets the audio data be stored and transmitted by a wider variety of media. Digital recording stores audio as a series of binary numbers (zeros and ones) representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate high enough to convey all sounds capable of being heard . A digital audio signal must be reconverted to analog form during playback before it
18360-651: The most demanding professional applications. New applications such as internet radio and podcasting have appeared. Technological developments in recording, editing, and consuming have transformed the record , movie and television industries in recent decades. Audio editing became practicable with the invention of magnetic tape recording , but technologies like MIDI , sound synthesis and digital audio workstations allow greater control and efficiency for composers and artists. Digital audio techniques and mass storage have reduced recording costs such that high-quality recordings can be produced in small studios. Today,
18513-402: The moving tape. In playback mode, the signal path is reversed, the tape head acting as a miniature electric generator as the varyingly magnetized tape passes over it. The original solid steel ribbon was replaced by a much more practical coated paper tape, but acetate soon replaced paper as the standard tape base. Acetate has fairly low tensile strength and if very thin it will snap easily, so it
18666-599: The next few years, the lesser record companies licensed or developed other electrical recording systems. By 1929 only the budget label Harmony was still issuing new recordings made by the old acoustical process. Comparison of some surviving Western Electric test recordings with early commercial releases indicates that the record companies artificially reduced the frequency range of recordings so they would not overwhelm non-electronic playback equipment, which reproduced very low frequencies as an unpleasant rattle and rapidly wore out discs with strongly recorded high frequencies. In
18819-488: The next two years, Blumlein developed stereo microphones and a stereo disc-cutting head, and recorded a number of short films with stereo soundtracks. In the 1930s, experiments with magnetic tape enabled the development of the first practical commercial sound systems that could record and reproduce high-fidelity stereophonic sound . The experiments with stereo during the 1930s and 1940s were hampered by problems with synchronization. A major breakthrough in practical stereo sound
18972-405: The only issued electrical recording. Several record companies and independent inventors, notably Orlando Marsh , experimented with equipment and techniques for electrical recording in the early 1920s. Marsh's electrically recorded Autograph Records were already being sold to the public in 1924, a year before the first such offerings from the major record companies, but their overall sound quality
19125-416: The paleophone. Though no trace of a working paleophone was ever found, Cros is remembered by some historians as an early inventor of a sound recording and reproduction machine. The first practical sound recording and reproduction device was the mechanical phonograph cylinder , invented by Thomas Edison in 1877 and patented in 1878. The invention soon spread across the globe and over the next two decades
19278-665: The playback volume of the three audio channels. Because of the complex equipment this system required, Disney exhibited the movie as a roadshow, and only in the United States. Regular releases of the movie used standard mono optical 35 mm stock until 1956, when Disney released the film with a stereo soundtrack that used the Cinemascope four-track magnetic sound system. German audio engineers working on magnetic tape developed stereo recording by 1941. Of 250 stereophonic recordings made during WW2, only three survive: Beethoven's 5th Piano Concerto with Walter Gieseking and Arthur Rother,
19431-428: The principle, now known as Faraday's law of induction , that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy. Faraday's disc was inefficient and of no use as
19584-808: The process of making a recording is separated into tracking, mixing and mastering . Multitrack recording makes it possible to capture signals from several microphones, or from different takes to tape, disc or mass storage allowing previously unavailable flexibility in the mixing and mastering stages. There are many different digital audio recording and processing programs running under several computer operating systems for all purposes, ranging from casual users and serious amateurs working on small projects to professional sound engineers who are recording albums, film scores and doing sound design for video games . Digital dictation software for recording and transcribing speech has different requirements; intelligibility and flexible playback facilities are priorities, while
19737-549: The public, with little fanfare, was of November 11, 1920, funeral service for The Unknown Warrior in Westminster Abbey , London. The recording engineers used microphones of the type used in contemporary telephones. Four were discreetly set up in the abbey and wired to recording equipment in a vehicle outside. Although electronic amplification was used, the audio was weak and unclear, as only possible in those circumstances. For several years, this little-noted disc remained
19890-590: The recording industry. Tape made possible the first sound recordings totally created by electronic means, opening the way for the bold sonic experiments of the Musique Concrète school and avant-garde composers like Karlheinz Stockhausen , which in turn led to the innovative pop music recordings of artists such as the Beatles and the Beach Boys . The ease and accuracy of tape editing, as compared to
20043-540: The recording process. These included improved microphones and auxiliary devices such as electronic filters, all dependent on electronic amplification to be of practical use in recording. In 1906, Lee De Forest invented the Audion triode vacuum tube, an electronic valve that could amplify weak electrical signals. By 1915, it was in use in long-distance telephone circuits that made conversations between New York and San Francisco practical. Refined versions of this tube were
20196-646: The rights to the Blattnerphone, and newly developed Marconi-Stille recorders were installed in the BBC's Maida Vale Studios in March 1935. The tape used in Blattnerphones and Marconi-Stille recorders was the same material used to make razor blades, and not surprisingly the fearsome Marconi-Stille recorders were considered so dangerous that technicians had to operate them from another room for safety. Because of
20349-466: The sale of consumer high-fidelity sound systems from the 1960s onward. In the 1950s, most record players were monophonic and had relatively low sound quality. Few consumers could afford high-quality stereophonic sound systems. In the 1960s, American manufacturers introduced a new generation of modular hi-fi components — separate turntables, pre-amplifiers, amplifiers, both combined as integrated amplifiers, tape recorders, and other ancillary equipment like
20502-505: The same tape many times, sounds could be duplicated from tape to tape with only minor loss of quality, and recordings could now be very precisely edited by physically cutting the tape and rejoining it. Within a few years of the introduction of the first commercial tape recorder—the Ampex 200 model, launched in 1948—American musician-inventor Les Paul had invented the first multitrack tape recorder , ushering in another technical revolution in
20655-514: The same time, sound recordings enabled music lovers outside the West to hear the most famous North American and European groups and singers. As digital recording developed, so did a controversy commonly known as the analog versus digital controversy. Audio professionals, audiophiles, consumers, musicians alike contributed to the debate based on their interaction with the media and the preferences for analog or digital processes. Scholarly discourse on
20808-566: The sound quality was poor, so between the wars, they were primarily used for voice recording and marketed as business dictating machines. In 1924, a German engineer, Kurt Stille, improved the Telegraphone with an electronic amplifier. The following year, Ludwig Blattner began work that eventually produced the Blattnerphone, which used steel tape instead of wire. The BBC started using Blattnerphones in 1930 to record radio programs. In 1933, radio pioneer Guglielmo Marconi 's company purchased
20961-454: The special property that it is conservative , which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated. The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage. For practical purposes, defining
21114-479: The system and both made their earliest published electrical recordings in February 1925, but neither actually released them until several months later. To avoid making their existing catalogs instantly obsolete, the two long-time archrivals agreed privately not to publicize the new process until November 1925, by which time enough electrically recorded repertory would be available to meet the anticipated demand. During
21267-495: The two ears. This discovery was commercialized in 1890 with the Théâtrophone system, which operated for over forty years until 1932. In 1931, Alan Blumlein , a British electronics engineer working for EMI , designed a way to make the sound of an actor in a film follow his movement across the screen. In December 1931, he submitted a patent application including the idea, and in 1933 this became UK patent number 394,325 . Over
21420-418: The two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it. Ørsted's words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too. Ørsted did not fully understand his discovery, but he observed
21573-615: The two used in stereo) and four speakers to create a 360-degree audio field around the listener. Following the release of the first consumer 4-channel hi-fi systems, a number of popular albums were released in one of the competing four-channel formats; among the best known are Mike Oldfield 's Tubular Bells and Pink Floyd 's The Dark Side of the Moon . Quadraphonic sound was not a commercial success, partly because of competing and somewhat incompatible four-channel sound systems (e.g., CBS , JVC , Dynaco and others all had systems) and generally poor quality, even when played as intended on
21726-450: The use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth (or lamellae ) of a steel comb. The fairground organ , developed in 1892, used a system of accordion-folded punched cardboard books. The player piano , first demonstrated in 1876, used a punched paper scroll that could store a long piece of music. The most sophisticated of the piano rolls were "hand-played," meaning that they were duplicates from
21879-566: The use of mechanical analogs of electrical circuits and developed a superior "rubber line" recorder for cutting the groove into the wax master in the disc recording system. By 1924, such dramatic progress had been made that Western Electric arranged a demonstration for the two leading record companies, the Victor Talking Machine Company and the Columbia Phonograph Company . Both soon licensed
22032-417: The vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together. Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces,
22185-549: Was 78.26 rpm in America and 77.92 rpm throughout the rest of the world. The difference in speeds was due to the difference in the cycle frequencies of the AC electricity that powered the stroboscopes used to calibrate recording lathes and turntables. The nominal speed of the disc format gave rise to its common nickname, the "seventy-eight" (though not until other speeds had become available). Discs were made of shellac or similar brittle plastic-like materials, played with needles made from
22338-414: Was acceptable. The compact 45 format required very little material. Vinyl offered improved performance, both in stamping and in playback. Vinyl records were, over-optimistically, advertised as "unbreakable". They were not, but they were much less fragile than shellac, which had itself once been touted as "unbreakable" compared to wax cylinders. Sound recording began as a purely mechanical process. Except for
22491-543: Was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves. A hollow conducting body carries all its charge on its outer surface. The field
22644-507: Was further improved just after World War II by American audio engineer John T. Mullin with backing from Bing Crosby Enterprises. Mullin's pioneering recorders were modifications of captured German recorders. In the late 1940s, the Ampex company produced the first tape recorders commercially available in the US. Magnetic tape brought about sweeping changes in both radio and the recording industry. Sound could be recorded, erased and re-recorded on
22797-530: Was in turn eventually superseded by polyester. This technology, the basis for almost all commercial recording from the 1950s to the 1980s, was developed in the 1930s by German audio engineers who also rediscovered the principle of AC biasing (first used in the 1920s for wire recorders ), which dramatically improved the frequency response of tape recordings. The K1 Magnetophon was the first practical tape recorder, developed by AEG in Germany in 1935. The technology
22950-411: Was introduced by RCA Victor in 1949. In the US and most developed countries, the two new vinyl formats completely replaced 78 rpm shellac discs by the end of the 1950s, but in some corners of the world, the 78 lingered on far into the 1960s. Vinyl was much more expensive than shellac, one of the several factors that made its use for 78 rpm records very unusual, but with a long-playing disc the added cost
23103-448: Was made by Bell Laboratories , who in 1937 demonstrated a practical system of two-channel stereo, using dual optical sound tracks on film. Major movie studios quickly developed three-track and four-track sound systems, and the first stereo sound recording for a commercial film was made by Judy Garland for the MGM movie Listen, Darling in 1938. The first commercially released movie with
23256-479: Was small cartridge-based tape systems, of which the compact cassette , commercialized by the Philips electronics company in 1964, is the best known. Initially a low-fidelity format for spoken-word voice recording and inadequate for music reproduction, after a series of improvements it entirely replaced the competing consumer tape formats: the larger 8-track tape (used primarily in cars). The compact cassette became
23409-410: Was too low to demonstrate any obvious advantage over traditional acoustical methods. Marsh's microphone technique was idiosyncratic and his work had little if any impact on the systems being developed by others. Telephone industry giant Western Electric had research laboratories with material and human resources that no record company or independent inventor could match. They had the best microphone,
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