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Audio level compression - Wikipedia, the free encyclopedia Audio level compression, also called dynamic range compression, volume compression, compression, or limiting, is a process that manipulates the dynamic range of an audio signal. Compression is used during sound recording, live sound reinforcement, and broadcasting to improve the perceived volume of audio. Compression is used extensively in this manner in broadcasting to boost the perceived volume of the sound track while keeping it within strict limits (broadcasters in most countries have legal limits on instantaneous peak volume they may broadcast). en.wikipedia.org /wiki/Audio_level_compression   (1497 words)

Ear protection and hearing device - Patent 3952158 As an example of operation of compression amplifier 28, it is assumed that a voice signal and a noise signal are passed simultaneously through filter 26 to the input of compression amplifier 28. It is further assumed that the amplitude of the voice signal is 10 units and the amplitude of the noise signal is 500 units at the input of compression amplifier 28. The output of compression amplifier 28 is connected as an input to power amplifier 30, which boosts the output of compression amplifier 28 to a level suitable for driving speaker 38 to a reasonable listening level within ear protectors 10 and 12. www.freepatentsonline.com /3952158.html   (1589 words)

Pulse-code modulation - Wikipedia, the free encyclopedia The default encoding on a DS0 is either μ-law (mu-law) PCM (North America and Japan) or A-law PCM (Europe and most of the rest of the world). These are logarithmic compression systems where a 12 or 13 bit linear PCM sample number is mapped into an 8 bit value. Later it was found that even further compression was possible and additional standards were published. en.wikipedia.org /wiki/Pulse-code_modulation   (1439 words)

Compression   (Site not responding. Last check: 2007-10-24) Compression (bit rate) may be reversible compression, lossless or it may be irreversible compression, lossy. Advantage is taken of the subtended viewing angle for the intended display, the perceptual characteristics of human vision, the statistics of image populations, and the objectives of the display. The compression ratio should not be used as the only method to assess the quality of a compressed signal. www.screensound.gov.au /glossary.nsf/Pages/Compression?OpenDocument   (726 words)

Spectwarper Spectwarper is fairly similiar to compander; however, unlike compander which compands bins against the constant peak of an input response file, spectwarper compands bins using a peak drawn (in the current frame) from a narrow frequency band centered around the value being processed. Unlike compander which only reduces the amplitude above the threshold when compressing, spectwarper reduces the amplitude of the entire range, becoming, in effect, an expander of the strongest amplitudes that expands them (when the compression level is severe) out of the picture. In this, the sucessive FFT frames have their amplitudes remapped by the identity function, similiarly expanding or compressing the dynamic range depending upon the warp specified; 0 (linear warp function) leaves the amplitudes unchanged. www.waveformsoftware.com /PVCX/PVCX_Help/Spectwarper.htm   (1768 words)

Do digital compression create aliasing ? - Hydrogenaudio Forums If the frequency's amplitude is 0.6, that's 0.2 in frame 1 and 0.4 in frame 2, assuming the burst of frequency is localised in time to that portion of the window. I guess for multiband compression, where you first divide the spectrum into bands, it may be possible to apply the compression in each band then post-filter to remove frequencies that don't belong in that band and could be generated harmonics, thereby reducing their amplitude. Anyhow, although compression in the simplest form is indeed the same as adding harmonics (overtones) to the frequency spectrum, this might not be desirable coloration of the sound. www.hydrogenaudio.org /forums/index.php?showtopic=9492   (3463 words)

От MP3 к MP3Pro: «что новенького?» и «стоит ли?»   (Site not responding. Last check: 2007-10-24) Compression factor of the original signal depends on a degree of its «simplification»; good compression is achieved by «aggressive simplification» when the coder considers as insignificant a great many nuances. As for the quality of compressed audio materials (in lossy format), as could be understood from the article (or simply to be convinced by practice), it all depends on competence of the use of coders and on general approach to compression. The fact, that compressed into lossy-format audio, degrades in quality, in comparison to the quality of original digital data, is indisputable; however it is also indisputable, that the level of these losses is completely depends on the user. websound.ru /articles/technol/clarification_e.htm   (8463 words)

Information Systems Technology In a number of applications, a speech waveform is processed using phase dispersion and amplitude compression to reduce its peak-to-rms ratio so as to increase loudness and intelligibility while minimizing perceived distortion. The solution can also be used to drive the sine-wave amplitude modification for amplitude compression, and is coupled to the desired shaping of the speech spectrum. The new dispersion solution, when integrated with amplitude compression, results in a significant reduction in the peak-to-rms ratio of the speech waveform with acceptable loss in quality. www.ll.mit.edu /IST/pubs/assp91-tfq-abs.html   (174 words)

EVP When the file is decompressed by the recipient, this compression method replaces the data for the sections it removed with calculated values to restore the file. Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Using non-lossy compression, the uncompressed file is identical to the original file. www.billlonero.com /EVP/glossary.htm   (2362 words)

elements of effective hearing-aid performance An effective hearing aid should compensate for the perceptive distortions of the patient; it should provide a neutral base (flat insertion gain and low distortion) that doesn't bias the compensation processing; and it should be fitted to the hearing characteristics of the individual patient.  Fulfilling two out of three of these requirements is not enough. 1- The reduction of intensity contrasts by compression is sometimes referred to in different terms: a loss of temporal modulation, a distortion of the temporal envelope, a violation of spectral integrity (when the contrasts are between sounds of different frequency), or a reduction of the modulation transfer function. Plomp, R. (1988).  The negative effect of amplitude compression in multichannel hearing aids in the light of the modulation transfer function.  Journal of the Acoustical Society of America 83, 2322-2327. www.audiologyonline.com /articles/pf_article_detail.asp?article_id=565   (1247 words)

Physics 4830 Experiment 0: Introduction to Digital Sound Editing   For example, very intense sounds are reduced in amplitude (compression) and very quiet sounds are increased in amplitude (expansion). Compression has been used in radio, since the early days because it makes a weak signal easier to hear and understand. Now, double the amplitude (as we did in last lab). www.colorado.edu /physics/phys4830/phys4830_fa01/lab/lab2.htm   (1388 words)

5aPP9   (Site not responding. Last check: 2007-10-24) The louder sensation due to temporal fluctuation was also found to be overall level-dependent: approaching peak amplitude loudness at a comfortably loud level, becoming less at lower sensation levels, and disappearing at higher levels. If this level-dependent loudness effect were related to the nonlinear cochlear compression, then it would disappear in cochlear-impaired listeners because their nonlinear compression is presumably damaged. These results indicate that loudness of dynamic stimuli is governed by two different mechanisms: a retrocochlear temporal processing mechanism which is presumably preserved in both normal and cochlear-impaired listeners, and a cochlear mechanism which provides amplitude compression at high levels in normal listeners and is damaged in the cochlear-impaired listeners. www.ucihs.uci.edu /hesp/meetings/asa/asaloudnessmain.htm   (219 words)

Sound Energy The greater the amount of compression of each wave, the greater the amplitude and the greater the energy carried by the wave. Intensity of a sound depends on the amplitude (compression) of the waves. Amplitude of a sound wave can be compared to the height of a transverse wave. www.aisp.net /vster/sound9.htm   (386 words)

Digital signal processing hearing aid - Patent 6104822 The compressed vibrations from the outer hair cells are communicated to the inner hair cells and then through the afferant neural fibers to the brain. The compression process requires a means for measuring the power of the input signal and generating a dynamically varying gain as a function of this input power. As the number of compression bands increases, each with its own compression ratio and static gain, it is possible to view the compressor as having an almost continuously varying compression ratio as a function of frequency. www.freepatentsonline.com /6104822.html   (12647 words)

Zhu and Steinberg, May 1997   (Site not responding. Last check: 2007-10-24) The measured data were obtained by recording the pulse signals on each element of a linear array that was moved in elevation to synthesize a two-dimensional aperture. The use of a novel amplitude compression that approaches inverse filtering improves the performance of the compensation techniques significantly. With the amplitude compression method, the results of the one-way experiments show that the mainlobe shape can be recovered down to -30 dB. www.ieee-uffc.org /archive/uffc/trans/Toc/abs/97/uf970575.htm   (270 words)

Video processor employing variable amplitude compression of the chrominance component (US4316213)   (Site not responding. Last check: 2007-10-24) A composite video signal is separated into luminance and chrominance components which are processed in separate channels having transfer functions which differ in terms of frequency response and large signal amplitude response. The chrominance channel exhibits a substantially uniform amplitude response and a variable compression characteristic dependent upon the chrominance signal level, a sum of chrominance and processed luminance signals or a composite output signal formed by a sum of processed chrominance and processed luminance signals. The composite signal is suitable for application to a picture carrier frequency modulator whereby an FM signal is produced suitable for video disc or tape recording and in which a tendency for luminance-chrominance crosstalk or interference is minimized. www.delphion.com /details?pn=US04316213__   (394 words)

Department of Computer Science and Electrical Engineering -- Events For example, multichannel amplitude compression processing is used to reduce the level variations of speech to fit the reduced dynamic ranges of listeners with sensorineural hearing loss. We present an amplitude compression algorithm based on a sinusoidal speech model that preserves the important spectral peaks. The algorithm provides fast-acting compression without artifacts, has time-varying frequency channels, and is computationally inexpensive. www.cs.umbc.edu /events/0405/rutledge.html   (445 words)

enhance: Manual Page   (Site not responding. Last check: 2007-10-24) -c mulaw Perform amplitude compression on the signal. A mu-law compression function is used: Select compression-style enhancement using a mu-law compression function: output_energy = log(1+mu.input_energy)/log(1+mu). A mu value of 10 gives modest compression. www.phon.ucl.ac.uk /resource/sfs/help/man/enhance.htm   (160 words)

Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations FINITE AMPLITUDE COMPRESSION WAVES IN A COLLISION-FREE PLASMA These are then used in a study of finite amplitude compression waves, which is built around the consideration of a magnetic piston problem.'' The asymptotic behavior of small amplitude waves is considered. It is found to give a simple but qualitatively correct picture of how the flows depend upon the two parameters theta, the angle the initial magnetic field makes with the direction of wave propagation, and epsilon, the electron-ion mass ratio. www.osti.gov /energycitations/product.biblio.jsp?osti_id=4004793   (347 words)

Art Pro VLA   (Site not responding. Last check: 2007-10-24) It is used for amplitude level compression and leveling (smoothing). It uses soft knee compression for level out transient peaks and is capable of creating a very "Squishy" sound. Which the sound level is keep pretty close to the maximum amplitude possible. www.kellyindustries.com /microphones/art_pro_vla.html   (194 words)

Channel Settings Sets the vertical (amplitude) compression / expansion for the trace. A positive number will compress and a negative number expand the data. A number between 20 and 50 should be fine for amplitude triggering and 2 to 4 for STA/LTA triggering. psn.quake.net /sdrdocs/chanset.htm   (1204 words)

Guide to F-Term Search System   (Site not responding. Last check: 2007-10-24) - DD11 Compression and expansion characteristics, or predistortion characteristics - DD12 Linear logarithmic compression and expansion characteristics - DD24 Cascade configurations of compression and expansion or predistortion circuits cxp.paterra.com /fterm5K066DD000.html   (183 words)

Wavelet-Based Noise Reduction And Compression For Hearing Aids (ResearchIndex) Wavelet-Based Noise Reduction and Compression for Hearing Aids (1999) Abstract: : Several wavelet-based methods have been applied to compensate the speech signal to improve the intelligibility for a common hearing impairment known as recruitment of loudness, a sensorineural hearing loss of cochlear origin. The more complete method performs both denoising and amplitude compression using the same wavelet coefficients for both stages. citeseer.ist.psu.edu /233440.html   (250 words)

Amazon.com: Hearing Aids--A Review of Past Research on Linear Amplification, Amplitude Compression, and Frequency ...   (Site not responding. Last check: 2007-10-24) Amazon.com: Hearing Aids--A Review of Past Research on Linear Amplification, Amplitude Compression, and Frequency Lowering (American Speech-Language): Books: Massachusetts Institute of Technology. This item is not eligible for Amazon Prime, but over a million other items are. I own the rights to this title and would like to make it available again through Amazon. www.amazon.com /exec/obidos/tg/detail/-/9992803584?v=glance   (303 words)

Patents 5586191 - 5586444 Patent 5586203: Method and apparatus for generating a halftone pattern for a multi-level output device Patent 5586225: Output apparatus and method for outputting a character using a run-length compressed font Patent 5586280: Method and apparatus for appending data to compressed records previously stored on a sequentially-accessible storage medium www.everypatent.com /idx/pdir1752.html   (8066 words)

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