Sound Sound The A-weighting curve is one of a family of curves defined in IEC179 and various other standards for use in Sound level meters. Though originally intended only for the measurement of low-level sounds (around 40-phon) it is now commonly used for the measurement of industrial noise too when assessing potential hearing damage at high levels. It also finds widespread use in audio equipment measurement, though arguably it is not the most suitable weighting for this purpose. === Loudness measurements === A-weighting is only really valid for relatively quiet sounds and for pure tones as it is based on the 40-phon Fletcher-Munson curves which represented an early determination of the equal-loudness contour for human hearing. The B and C curves were intended for louder sounds (though they are less used) while the D curve is used in assessing loud aircraft noise ( IEC 537). Although the original Fletcher-Munson family of contours have been subject to fresh experimental determinations, notably by Robinson-Dadson, a recent survey by the ISO standards organisation suggests that the latter may have been less accurate than thought, and the survey comments that it is fortunate that in the latest standard set of contours, defined in ISO 226 (2003), the 40-phon curve comes closer to the original Fletcher-Munson, than to the Robinson-Dadson. Nevertheless, it will be noted that A-weighting would be a better match to the loudness curve if it fell much more steeply above 10kHz, and it must be assumed that a better match was not aimed for because steep filters were more dificult to construct in the early days of electronics. Nowadays, no such limitation need exist, as demonstrated by the ITU-R 468 curve. If weightings such as these are used without further band-limiting it is possible to obtain different readings on different instruments if ultrasonic noise is present. Good design therefore requires a 20kHz low-pass filter to be combined with the weighting curve. === Environmental noise measurement === A-weighted decibels are abbreviated dB(A) or dBA. When acoustic (calibrated microphone) measurements are being referred to, then the units used will be dB SPL ( sound pressure level) referenced to ...more on Wikipedia about "A-weighting"
A3D (Aureal 3-Dimensional) is a technology developed by Aureal that delivers sound with a three-dimensional effect through headphones, two or even four speakers. Many modern sound cards and PC games used to support this feature, but this number has stopped growing due to Aureal's demise. ...more on Wikipedia about "A3D"
Acoustic ecology is the relationship, mediated through sound, between living beings and their environment. Sometimes called soundscape ecology. Acoustic ecology studies started in the late 60's with R. Murray Schafer and his team at Simon Fraser University ( Vancouver, Canada) as part of the World Soundscape Project. The first study produced by the WSP was titled The Vancouver Soundscape. The interest in this area grew enormously after this pioneer and innovative study and the area of acoustic ecology raised the interesst of researchers and artists all over the world. In 1993 the members of the by now large and active international acoustic ecology community formed the World Forum of Acoustic Ecology ** . ...more on Wikipedia about "Acoustic ecology"
The digital audio standard frequently called AES/EBU, for Audio Engineering Society / European Broadcasting Union, that is officially known as AES3, was first published in 1992 as a standard (and revised in 1995, 1998, and 2003) for carrying digital audio signals between various devices. ...more on Wikipedia about "AES/EBU"
The AES11 standard published by the Audio Engineering Society provides a systematic approach to the synchronization of digital audio signals. Recommendations are made concerning the accuracy of sample clocks as embodied in the interface signal and the use of this format as a convenient synchronization reference where signals must be rendered co-timed for digital processing. Synchronism is defined, and limits are given which take account of relevant timing uncertainties encountered in ...more on Wikipedia about "AES11"
AES47 ( IEC 62365) is an open standard that specifies a method for packing AES3 professional digital audio streams over Asynchronous Transfer Mode networks. The details of these standards can be studied at the Audio Engineering Socity standards web site by downloading courtesy copies of AES47-2002, AES-R4-2002 and AES3-2003. The change in thinking from traditional ATM network design is not to necessarily use ATM to pass IP traffic (apart from management traffic) but to use it in parallel with standard Ethernet structures to deal with extremely high performance secure media streams. From work carried out at the British Broadcasting Corporation’s ( BBC) R&D department and published as White Paper 074 , it has been established that this approach provides the necessary performance for professional media production. AES47 has been developed to allow the simultaneous transport and switched distribution of a large number of AES3 linear audio streams at different sample frequencies. AES47 can support any of the standard AES3 sample rates and word size. AES11 Annex D shows an example method to provide isochronous timing relationships for distributed AES3 structures over asynchronous networks such as AES47 where reference signals may be locked to common timing sources such as GPS. ...more on Wikipedia about "AES47"
Ambisonics is a one point inphase recording and replay technique for coding and encoding sound information on a number of channels to reproduce a "3 dimensional" sound field. In the basic version, sound information is encoded into 4 channels: W, X, Y and Z. This is called the Ambisonics B-format. The W channel is the general mono level of the signal. The X, Y and Z channels are the directional components in three dimensions. These directional components are based on a spherical harmonic decomposition of the soundfield. The loudspeaker signals are derived by using a linear combination of these four channels and is dependent on the actual position of the speaker in relation to the center of an imaginary sphere going through all available speakers. ...more on Wikipedia about "Ambisonics"
Amplitude is a nonnegative scalar measure of a wave's magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ...more on Wikipedia about "Amplitude"
An analog or analogue signal is any variable signal continuous in both time and amplitude. It differs from a digital signal in that small fluctuations in the signal are meaningful. Analog is usually thought of in an electrical context, however mechanical, pneumatic, hydraulic, and other systems may also use analog signals. ...more on Wikipedia about "Analog signal"
of which 128 (at most) relative to the "minimum" signal level, which result in a dynamic range of just 48.165 dB, which is inferior to most cassette tape systems, and in fact 8-bit recordings tend to sound noisy and scratchy, and "miss" low-level signals. ...more on Wikipedia about "Analog sound vs. digital sound"
An anechoic room simulates a free field — a representation of a theoretical infinite space, in which there are no sound wave reflections ( echoes). In rooms such as these, the only sounds which exist are emitted directly from their source, and not reflected from another part of the chamber. Anechoic rooms have the characteristic of being muted, muffled, and silent. ...more on Wikipedia about "Anechoic room"
Audio can mean: ...more on Wikipedia about "Audio"
A serious and reliable measure of the power output of an audio amplifier, or the power handling of a loudspeaker is average power, commonly called watts RMS. RMS stands for root mean square and is actually a misnomer here but has nonetheless become the common term. The "RMS" power is found by averaging the instantaneous power output over a long period of time, so it is actually the average power or mean power. The term RMS is used due to the fact that the mean power is calculated from the RMS voltage and current (or one of them and the impedance). ...more on Wikipedia about "Audio power"
(Awkward silence) > > Category:Pages for deletion ...more on Wikipedia about "Awkward silence"
In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies. ...more on Wikipedia about "Beat (acoustics)"
A breakout box is usually a box, in which a compound electrical connector is separated or "broken out" into its component connectors. Compound connectors (which are often proprietary) are used where sufficient space for (or access to) connections is unavailable, such as on personal computer sound cards. If there are only a few connections, then a breakout cable may be used, as is common on smaller notebook computers. ...more on Wikipedia about "Breakout box"
A death rattle is a gurgling or rattle-like noise produced by the accumulation of excessive respiratory secretions in the throat. ...more on Wikipedia about "Death rattle"
The decibel (dB) is a measure of the ratio between two quantities, and is used in a wide variety of measurements in acoustics, physics and electronics. While originally only used for power and intensity ratios, it has come to be used more generally in engineering. The decibel is widely used as a measure of the loudness of sound. It is a " dimensionless unit" like percent. Decibels are useful because they allow even very large or small ratios to be represented with a conveniently small number. This is achieved by using a logarithm. ...more on Wikipedia about "Decibel"
In digital recording, the analog signal of a motion-picture/ sound is converted into a stream of discrete numbers, representing the changes in air pressure (chroma and luminace values in case of video) through time; thus making an abstract template for the original sound. ...more on Wikipedia about "Digital recording"
In relationship to Spectrum Analyzers the Displayed Average Noise Level (DANL), is directly associated with Amplitude Specifications in a given electronic signal, and the signals Noise-to-Noise ratios. ...more on Wikipedia about "Displayed average noise level"
The environmental audio extensions (or EAX) are a number of digital signal processing presets for audio, present in Creative Labs later Sound Blaster sound cards and the Creative NOMAD/ Creative Zen product lines. EAX displaced the alternative A3D (Aureal 3-Dimensional) in 2001. ...more on Wikipedia about "Environmental audio extensions"
FindSounds is a website run by the Comparisonics Corporation. It searches an index of over 1,000,000 sounds on the internet, with 100,000 users and 1,000,000 searches each month. The index mainly consists of sound effects and musical instrument samples. Results are in AIFF, AU and WAV formats, in both mono and stereo. ...more on Wikipedia about "FindSounds"
A formant is a peak in an acoustic frequency spectrum which results from the resonant frequencies of any acoustical system. It is most commonly invoked in phonetics or acoustics involving the resonant frequencies of vocal tracts or musical instruments. However, it is equally valid to talk about the formant frequencies of the air in a room, as exploited, for example, by Alvin Lucier in his piece I am sitting in a room. ...more on Wikipedia about "Formant"
Frequency is the measurement of the number of times that a repeated event occurs per unit time. It is also defined as the rate of change of phase of a sinusoidal waveform. ...more on Wikipedia about "Frequency"
Gobo is a slang term used by sound recording engineers to refer to a movable acoustic isolation panel. ...more on Wikipedia about "Gobo (recording)"
shortopedia Dreamteam. shortopedia
This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia . Direct links to the original articles are in the text.
If you use exact copy or modified of this article you should preserve above paragraph and put also : It uses material from
the Shortopedia article about "Sound".
| MAIN PAGE | MAIN INDEX | CONTACT US |