Misplaced Pages

#260739

36-608: Architectural acoustics can be about achieving good speech intelligibility in a theatre, restaurant or railway station, enhancing the quality of music in a concert hall or recording studio, or suppressing noise to make offices and homes more productive and pleasant places to work and live in. Architectural acoustic design is usually done by acoustic consultants. This science analyzes noise transmission from building exterior envelope to interior and vice versa. The main noise paths are roofs , eaves , walls , windows , door and penetrations. Sufficient control ensures space functionality and

72-473: A direction as well as a magnitude. The direction of sound intensity is the average direction in which energy is flowing. The average sound intensity during time T is given by ⟨ I ⟩ = 1 T ∫ 0 T p ( t ) v ( t ) d t . {\displaystyle \langle \mathbf {I} \rangle ={\frac {1}{T}}\int _{0}^{T}p(t)\mathbf {v} (t)\,\mathrm {d} t.} For

108-565: A concert hall or music recital space. To illustrate this concept consider the difference between a modern large office meeting room or lecture theater and a traditional classroom with all hard surfaces. Interior building surfaces can be constructed of many different materials and finishes. Ideal acoustical panels are those without a face or finish material that interferes with the acoustical infill or substrate. Fabric covered panels are one way to heighten acoustical absorption. Perforated metal also shows sound absorbing qualities. Finish material

144-451: A direction perpendicular to that area. The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m ). One application is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity. Sound intensity is not the same physical quantity as sound pressure . Human hearing is sensitive to sound pressure which is related to sound intensity. In consumer audio electronics,

180-627: A natural look to the interior space, although acoustical absorption may not be great. There are four ways to improve workplace acoustics and solve workplace sound problems – the ABCDs. Building services noise control is the science of controlling noise produced by: Inadequate control may lead to elevated sound levels within the space which can be annoying and reduce speech intelligibility. Typical improvements are vibration isolation of mechanical equipment, and sound attenuators in ductwork. Sound masking can also be created by adjusting HVAC noise to

216-630: A plane wave , I = 2 π 2 ν 2 δ 2 ρ c {\displaystyle \mathrm {I} =2\pi ^{2}\nu ^{2}\delta ^{2}\rho c} Where, For a spherical sound wave, the intensity in the radial direction as a function of distance r from the centre of the sphere is given by I ( r ) = P A ( r ) = P 4 π r 2 , {\displaystyle I(r)={\frac {P}{A(r)}}={\frac {P}{4\pi r^{2}}},} where Thus sound intensity decreases as 1/ r from

252-409: A predetermined level. Intelligibility (communication) In speech communication, intelligibility is a measure of how comprehensible speech is in given conditions. Intelligibility is affected by the level (loud but not too loud) and quality of the speech signal, the type and level of background noise, reverberation (some reflections but not too many), and, for speech over communication devices,

288-506: A room is influenced by the Intelligibility is negatively impacted by background noise and too much reverberation. The relationship between sound and noise levels is generally described in terms of a signal-to-noise ratio. With a background noise level between 35 and 100 dB, the threshold for 100% intelligibility is usually a signal-to-noise ratio of 12 dB. 12 dB means that the signal should be roughly 4 times louder than

324-408: A room's surfaces based on sound absorbing and reflecting properties. Excessive reverberation time , which can be calculated, can lead to poor speech intelligibility. Sound reflections create standing waves that produce natural resonances that can be heard as a pleasant sensation or an annoying one. Reflective surfaces can be angled and coordinated to provide good coverage of sound for a listener in

360-502: A simplified syntax and a small and easier-to-understand vocabulary than speech directed to adults Compared to adult directed speech, it has a higher fundamental frequency, exaggerated pitch range, and slower rate. Citation speech occurs when people engage self-consciously in spoken language research. It has a slower tempo and fewer connected speech processes (e.g., shortening of nuclear vowels, devoicing of word-final consonants) than normal speech. Hyperspace speech, also known as

396-1180: A sound intensity p-u probe comprising a microphone and a particle velocity sensor , or estimated indirectly by using a p-p probe that approximates the particle velocity by integrating the pressure gradient between two closely spaced microphones. Pressure-based measurement methods are widely used in anechoic conditions for noise quantification purposes. The bias error introduced by a p-p probe can be approximated by I ^ n p − p ≃ I n − φ pe p rms 2 k Δ r ρ c = I n ( 1 − φ pe k Δ r p rms 2 / ρ c I r ) , {\displaystyle {\widehat {I}}_{n}^{p-p}\simeq I_{n}-{\frac {\varphi _{\text{pe}}\,p_{\text{rms}}^{2}}{k\Delta r\rho c}}=I_{n}\left(1-{\frac {\varphi _{\text{pe}}}{k\Delta r}}{\frac {p_{\text{rms}}^{2}/\rho c}{I_{r}}}\right),} where I n {\displaystyle I_{n}}

SECTION 10

#1732802343261

432-435: A variable or modulated background noise such as competing speech, multi-talker or "cocktail party" babble, or industrial machinery. Reverberation also affects the speech signal by blurring speech sounds over time. This has the effect of enhancing vowels with steady states, while masking stops, glides and vowel transitions, and prosodic cues such as pitch and duration. The fact that background noise compromises intelligibility

468-496: Is I 0 = 1   p W / m 2 . {\displaystyle I_{0}=1~\mathrm {pW/m^{2}} .} being approximately the lowest sound intensity hearable by an undamaged human ear under room conditions. The proper notations for sound intensity level using this reference are L I /(1 pW/m ) or L I (re 1 pW/m ) , but the notations dB SIL , dB(SIL) , dBSIL, or dB SIL are very common, even if they are not accepted by

504-527: Is exploited in audiometric testing involving spoken speech and some linguistic perception experiments as a way to compensate for the ceiling effect by making listening tasks more difficult. Word articulation remains high even when only 1–2% of the wave is unaffected by distortion. The human brain automatically changes speech made in noise through a process called the Lombard effect . Such speech has increased intelligibility compared to normal speech. It

540-440: Is not only louder but the frequencies of its phonetic fundamental are increased and the durations of its vowels are prolonged. People also tend to make more noticeable facial movements. Shouted speech is less intelligible than Lombard speech because increased vocal energy produces decreased phonetic information. However, "infinite peak clipping of shouted speech makes it almost as intelligible as normal speech." Clear speech

576-620: Is often required based on building use and local municipal codes. An example would be providing a suitable design for a home which is to be constructed close to a high volume roadway, or under the flight path of a major airport, or of the airport itself. The science of limiting and/or controlling noise transmission from one building space to another to ensure space functionality and speech privacy. The typical sound paths are ceilings, room partitions, acoustic ceiling panels (such as wood dropped ceiling panels), doors , windows , flanking, ducting and other penetrations. Technical solutions depend on

612-452: Is the p-u phase mismatch introduced by calibration errors. Therefore, the phase calibration is critical when measurements are carried out under near field conditions, but not so relevant if the measurements are performed out in the far field. The “reactivity” (the ratio of the reactive to the active intensity) indicates whether this source of error is of concern or not. Compared to pressure-based probes, p-u intensity probes are unaffected by

648-460: Is the biased estimate obtained using a p-u probe, P {\displaystyle P} and V n {\displaystyle V_{n}} are the Fourier transform of sound pressure and particle velocity, J n {\displaystyle J_{n}} is the reactive intensity and φ ue {\displaystyle \varphi _{\text{ue}}}

684-663: Is the reference sound pressure. For a progressive spherical wave, p c = z 0 , {\displaystyle {\frac {p}{c}}=z_{0},} where z 0 is the characteristic specific acoustic impedance . Thus, I 0 = p 0 2 I p 2 = p 0 2 p c p 2 = p 0 2 z 0 . {\displaystyle I_{0}={\frac {p_{0}^{2}I}{p^{2}}}={\frac {p_{0}^{2}pc}{p^{2}}}={\frac {p_{0}^{2}}{z_{0}}}.} In air at ambient temperature, z 0 = 410 Pa·s/m , hence

720-426: Is the wave number, ρ {\displaystyle \rho } is the density of air, c {\displaystyle c} is the speed of sound and Δ r {\displaystyle \Delta r} is the spacing between the two microphones. This expression shows that phase calibration errors are inversely proportional to frequency and microphone spacing and directly proportional to

756-408: Is the “true” intensity (unaffected by calibration errors), I ^ n p − p {\displaystyle {\hat {I}}_{n}^{p-p}} is the biased estimate obtained using a p-p probe, p rms {\displaystyle p_{\text{rms}}} is the root-mean-squared value of the sound pressure, k {\displaystyle k}

SECTION 20

#1732802343261

792-405: Is to make the crowd as loud as possible and inter-space noise control becomes a factor but in helping reflect noise to create more reverberation and louder decibel level throughout the stadium. Many outdoor soccer stadiums for example have roofs over the fan sections which create more reverberation and echoing which helps raise the general volume in the stadium. This is the science of controlling

828-399: Is used to cover over the acoustical substrate. Mineral fiber board, or Micore , is a commonly used acoustical substrate. Finish materials often consist of fabric, wood or acoustical tile. Fabric can be wrapped around substrates to create what is referred to as a "pre-fabricated panel" and often provides good noise absorption if laid onto a wall. Prefabricated panels are limited to the size of

864-419: Is used when talking to a person with a hearing impairment . It is characterized by a slower speaking rate, more and longer pauses, elevated speech intensity, increased word duration, "targeted" vowel formants, increased consonant intensity compared to adjacent vowels, and a number of phonological changes (including fewer reduced vowels and more released stop bursts). Infant-directed speech—or baby talk —uses

900-576: The SI. The reference sound intensity I 0 is defined such that a progressive plane wave has the same value of sound intensity level (SIL) and sound pressure level (SPL), since I ∝ p 2 . {\displaystyle I\propto p^{2}.} The equality of SIL and SPL requires that I I 0 = p 2 p 0 2 , {\displaystyle {\frac {I}{I_{0}}}={\frac {p^{2}}{p_{0}^{2}}},} where p 0 = 20 μPa

936-428: The background noise. The speech signal ranges from about 200–8000 Hz, while human hearing ranges from about 20-20,000 Hz, so the effects of masking depend on the frequency range of the masking noise. Additionally, different speech sounds make use of different parts of the speech frequency spectrum, so a continuous background noise such as white or pink noise will have a different effect on intelligibility than

972-1064: The centre of the sphere: I ( r ) ∝ 1 r 2 . {\displaystyle I(r)\propto {\frac {1}{r^{2}}}.} This relationship is an inverse-square law . Sound intensity level (SIL) or acoustic intensity level is the level (a logarithmic quantity ) of the intensity of a sound relative to a reference value. It is denoted L I , expressed in nepers , bels , or decibels , and defined by L I = 1 2 ln ⁡ ( I I 0 ) N p = log 10 ⁡ ( I I 0 ) B = 10 log 10 ⁡ ( I I 0 ) d B , {\displaystyle L_{I}={\frac {1}{2}}\ln \left({\frac {I}{I_{0}}}\right)\mathrm {Np} =\log _{10}\left({\frac {I}{I_{0}}}\right)\mathrm {B} =10\log _{10}\left({\frac {I}{I_{0}}}\right)\mathrm {dB} ,} where The commonly used reference sound intensity in air

1008-430: The hyperspace effect, occurs when people are misled about the presence of environment noise. It involves modifying the formants F1 and F2 of phonetic vowel targets to ease perceived difficulties on the part of the listener in recovering information from the acoustic signal. Sound intensity level Sound intensity , also known as acoustic intensity , is defined as the power carried by sound waves per unit area in

1044-471: The level differences are called "intensity" differences, but sound intensity is a specifically defined quantity and cannot be sensed by a simple microphone. Sound intensity level is a logarithmic expression of sound intensity relative to a reference intensity. Sound intensity, denoted I , is defined by I = p v {\displaystyle \mathbf {I} =p\mathbf {v} } where Both I and v are vectors , which means that both have

1080-908: The other hand, the bias error introduced by a p-u probe can be approximated by I ^ n p − u = 1 2 Re ⁡ { P V ^ n ∗ } = 1 2 Re ⁡ { P V n ∗ e − j φ ue } ≃ I n + φ ue J n , {\displaystyle {\hat {I}}_{n}^{p-u}={\frac {1}{2}}\operatorname {Re} \left\{{P{\hat {V}}_{n}^{*}}\right\}={\frac {1}{2}}\operatorname {Re} \left\{{PV_{n}^{*}e^{-j\varphi _{\text{ue}}}}\right\}\simeq I_{n}+\varphi _{\text{ue}}J_{n}\,,} where I ^ n p − u {\displaystyle {\hat {I}}_{n}^{p-u}}

1116-487: The properties of the communication system. A common standard measurement for the quality of the intelligibility of speech is the Speech Transmission Index (STI) . The concept of speech intelligibility is relevant to several fields, including phonetics , human factors , acoustical engineering , and audiometry . Speech is considered to be the major method of communication between humans. Humans alter

Architectural acoustics - Misplaced Pages Continue

1152-419: The ratio of the mean square sound pressure to the sound intensity. If the pressure-to-intensity ratio is large then even a small phase mismatch will lead to significant bias errors. In practice, sound intensity measurements cannot be performed accurately when the pressure-intensity index is high, which limits the use of p-p intensity probes in environments with high levels of background noise or reflections. On

1188-559: The reference value I 0 = 1 pW/m . In an anechoic chamber which approximates a free field (no reflection) with a single source, measurements in the far field in SPL can be considered to be equal to measurements in SIL. This fact is exploited to measure sound power in anechoic conditions. Sound intensity is defined as the time averaged product of sound pressure and acoustic particle velocity. Both quantities can be directly measured by using

1224-504: The source of the noise and the path of acoustic transmission , for example noise by steps or noise by (air, water) flow vibrations. An example would be providing suitable party wall design in an apartment complex to minimize the mutual disturbance due to noise by residents in adjacent apartments. Inter-space noise control can take a different form when talking about Acoustics in European football stadiums. One goal in stadium acoustics

1260-696: The substrate ranging from 2 by 4 feet (0.61 m × 1.22 m) to 4 by 10 feet (1.2 m × 3.0 m). Fabric retained in a wall-mounted perimeter track system, is referred to as "on-site acoustical wall panels". This is constructed by framing the perimeter track into shape, infilling the acoustical substrate and then stretching and tucking the fabric into the perimeter frame system. On-site wall panels can be constructed to accommodate door frames, baseboard, or any other intrusion. Large panels (generally, greater than 50 square feet (4.6 m)) can be created on walls and ceilings with this method. Wood finishes can consist of punched or routed slots and provide

1296-403: The way they speak and hear according to many factors, like the age, gender, native language and social relationship between talker and listener. Speech intelligibility may also be affected by pathologies such as speech and hearing disorders. Finally, speech intelligibility is influenced by the environment or limitations on the communication channel. How well a spoken message can be understood in

#260739