The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period ). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplitude (see below), which are all functions of the magnitude of the differences between the variable's extreme values . In older texts, the phase of a periodic function is sometimes called the amplitude.
27-503: ADSR may refer to: ADSR envelope (attack–decay–sustain–release), a common type of music envelope Accelerator-driven subcritical reactor , a nuclear reactor using a particle accelerator to generate a fission reaction in a sub-critical assembly of fissionable material Attack Decay Sustain Release , the debut album from Simian Mobile Disco, released on 18 June 2007 Topics referred to by
54-505: A delay parameter before the attack . Modern synthesizers, such as the Prophet '08 , have DADSR (delay, attack, decay, sustain, release) envelopes. The delay setting determines the length of silence between hitting a note and the attack. Some software synthesizers , such as Image-Line's 3xOSC (included with their DAW FL Studio ) have DAHDSR (delay, attack, hold, decay, sustain, release) envelopes. A common feature on many synthesizers
81-462: A hold time parameter; the sustain level is not programmable. Another common variation in the same vein is the AHDSR (attack, hold, decay, sustain, release) envelope, in which the hold parameter controls how long the envelope stays at full volume before entering the decay phase. Multiple attack, decay and release settings may be found on more sophisticated models. Certain synthesizers also allow for
108-517: A square wave, or a triangle wave. For an asymmetric wave (periodic pulses in one direction, for example), the peak amplitude becomes ambiguous. This is because the value is different depending on whether the maximum positive signal is measured relative to the mean, the maximum negative signal is measured relative to the mean, or the maximum positive signal is measured relative to the maximum negative signal (the peak-to-peak amplitude ) and then divided by two (the semi-amplitude ). In electrical engineering,
135-568: A transient loudness attack, decay, sustain, and release. With waveforms containing many overtones, complex transient timbres can be achieved by assigning each overtone to its own distinct transient amplitude envelope. Unfortunately, this has the effect of modulating the loudness of the sound as well. It makes more sense to separate loudness and harmonic quality to be parameters controlled independently of each other. To do so, harmonic amplitude envelopes are frame-by-frame normalized to become amplitude proportion envelopes, where at each time frame all
162-409: Is an AD envelope (attack and decay only). This can be used to control, for example, the pitch of one oscillator, which in turn may be synchronized with another oscillator by oscillator sync . Amplitude For symmetric periodic waves, like sine waves or triangle waves , peak amplitude and semi amplitude are the same. In audio system measurements , telecommunications and others where
189-398: Is dependent on waveform . If the wave shape being measured is greatly different from a sine wave, the relationship between RMS and average value changes. True RMS-responding meters were used in radio frequency measurements, where instruments measured the heating effect in a resistor to measure a current. The advent of microprocessor -controlled meters capable of calculating RMS by sampling
216-419: Is different from Wikidata All article disambiguation pages All disambiguation pages Envelope (music) In sound and music , an envelope describes how a sound changes over time. For example, a piano key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero. An envelope may relate to elements such as amplitude (volume), frequency (with
243-451: Is proportional to the square of the RMS amplitude (and not, in general, to the square of the peak amplitude). For alternating current electric power , the universal practice is to specify RMS values of a sinusoidal waveform. One property of root mean square voltages and currents is that they produce the same heating effect as a direct current in a given resistance. The peak-to-peak value
270-439: Is related to amplitude and intensity and is one of the most salient qualities of a sound, although in general sounds it can be recognized independently of amplitude . The square of the amplitude is proportional to the intensity of the wave. For electromagnetic radiation , the amplitude of a photon corresponds to the changes in the electric field of the wave. However, radio signals may be carried by electromagnetic radiation;
297-481: Is represented by a scalar. Other sounds can have percussive amplitude envelopes featuring an abrupt onset followed by an immediate exponential decay. Percussive amplitude envelopes are characteristic of various impact sounds: two wine glasses clinking together, hitting a drum, slamming a door, etc. where the amplitude is transient and must be represented as either a continuous function or a discrete vector. Percussive amplitude envelopes model many common sounds that have
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#1732772159040324-438: Is used, for example, when choosing rectifiers for power supplies, or when estimating the maximum voltage that insulation must withstand. Some common voltmeters are calibrated for RMS amplitude, but respond to the average value of a rectified waveform. Many digital voltmeters and all moving coil meters are in this category. The RMS calibration is only correct for a sine wave input since the ratio between peak, average and RMS values
351-454: The measurand is a signal that swings above and below a reference value but is not sinusoidal , peak amplitude is often used. If the reference is zero, this is the maximum absolute value of the signal; if the reference is a mean value ( DC component ), the peak amplitude is the maximum absolute value of the difference from that reference. Semi-amplitude means half of the peak-to-peak amplitude. The majority of scientific literature employs
378-506: The square root of the mean over time of the square of the vertical distance of the graph from the rest state; i.e. the RMS of the AC waveform (with no DC component ). For complicated waveforms, especially non-repeating signals like noise, the RMS amplitude is usually used because it is both unambiguous and has physical significance. For example, the average power transmitted by an acoustic or electromagnetic wave or by an electrical signal
405-434: The amplitude is a displacement . The amplitude of sound waves and audio signals (which relates to the volume) conventionally refers to the amplitude of the air pressure in the wave, but sometimes the amplitude of the displacement (movements of the air or the diaphragm of a speaker ) is described. The logarithm of the amplitude squared is usually quoted in dB , so a null amplitude corresponds to − ∞ dB. Loudness
432-418: The amplitude of frequency - and phase -modulated waveform envelopes . In this simple wave equation The units of the amplitude depend on the type of wave, but are always in the same units as the oscillating variable. A more general representation of the wave equation is more complex, but the role of amplitude remains analogous to this simple case. For waves on a string , or in a medium such as water ,
459-599: The control voltage determining pitch and the other to trigger the envelope generator. The envelope generator became a standard feature of synthesizers. Following discussions with the engineer and composer Vladimir Ussachevsky , the head of the Columbia-Princeton Electronic Music Center , in 1965, Moog developed a new envelope module whose functions were described in f T1 (attack time), T2 (initial decay time), ESUS (sustain level), and T3 (final decay time). These were later simplified to
486-508: The creator of the Moog synthesizer , in the 1960s. The composer Herbert Deutsch suggested Moog find a way to articulate his synthesizer so notes did not simply trigger on and off. Moog wired a doorbell button to the synthesizer and used a capacitor to store and slowly release voltage produced from hitting a key. He refined the design to remove the need to push a separate button with every keypress, with two switches on every key: one to produce
513-444: The intensity of the radiation ( amplitude modulation ) or the frequency of the radiation ( frequency modulation ) is oscillated and then the individual oscillations are varied (modulated) to produce the signal. Amplitude envelope refers to the changes in the amplitude of a sound over time, and is an influential property as it affects perception of timbre. A flat tone has a steady state amplitude that remains constant during time, which
540-466: The modern ADSR form (attack time, decay time, sustain level, release time) by ARP . The most common kind of envelope generator has four stages: attack, decay, sustain, and release (ADSR). While attack, decay, and release refer to time, sustain refers to level. Some electronic musical instruments can invert the ADSR envelope, reversing the behavior of the normal ADSR envelope. During the attack phase,
567-552: The modulated sound parameter fades from the maximum amplitude to zero then, during the decay phase, rises to the value specified by the sustain parameter. After the key has been released the sound parameter rises from sustain amplitude back to maximum amplitude. Some envelopes, such as that of the Korg MS-20 , have an extra parameter, hold. This holds notes at the sustain level for a fixed length of time before decaying. The General Instrument AY-3-8910 sound chip includes only
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#1732772159040594-405: The same term [REDACTED] This disambiguation page lists articles associated with the title ADSR . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=ADSR&oldid=1254786336 " Category : Disambiguation pages Hidden categories: Short description
621-409: The term amplitude or peak amplitude to mean semi-amplitude. It is the most widely used measure of orbital wobble in astronomy and the measurement of small radial velocity semi-amplitudes of nearby stars is important in the search for exoplanets (see Doppler spectroscopy ). In general, the use of peak amplitude is simple and unambiguous only for symmetric periodic waves, like a sine wave,
648-473: The use of filters ) or pitch . Envelope generators , which allow users to control the different stages of a sound, are common features of synthesizers , samplers , and other electronic musical instruments . The most common envelope generator is controlled with four parameters: attack , decay , sustain and release ( ADSR ). The envelope generator was created by the American engineer Robert Moog ,
675-572: The usual solution to this ambiguity is to measure the amplitude from a defined reference potential (such as ground or 0 V). Strictly speaking, this is no longer amplitude since there is the possibility that a constant ( DC component ) is included in the measurement. Peak-to-peak amplitude (abbreviated p–p or PtP or PtoP ) is the change between peak (highest amplitude value) and trough (lowest amplitude value, which can be negative). With appropriate circuitry, peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing
702-441: The waveform has made true RMS measurement commonplace. In telecommunications, pulse amplitude is the magnitude of a pulse parameter, such as the voltage level, current level, field intensity , or power level. Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as average , instantaneous , peak , or root-mean-square . Pulse amplitude also applies to
729-410: The waveform on an oscilloscope . Peak-to-peak is a straightforward measurement on an oscilloscope, the peaks of the waveform being easily identified and measured against the graticule . This remains a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate. Root mean square (RMS) amplitude is used especially in electrical engineering : the RMS is defined as
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