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Entries found for search: ESS

auxiliary messages : A classification of MIDI messages which includes Active Sensing, All Notes Off, Local On/Off, and Reset, and which describes whether the particular MIDI device responds to any of thsese messages.

compression : (1) The process of reducing the dynamic range of an audio signal by reducing the peaks so as to be able to boost the low levels. For every dB of compression applied, the S/N ratio is worsened by 1dB, assuming that the make-up gain is set so that the maximum levels of the compressed and uncompressed signals are the same, as the quieter parts of the original signal, plus any noise contained in these regions, will be raised in level. (2) A dynamic-range problem in loudspeakers caused by nonlinearity under conditions of high input power levels. At very high levels, the acoustic output increases more slowly or ceases to increase altogether as the input power increases, producing nonlinear distortion, i.e., a frequency response curve very different for very high levels. (3) Data compression used on digital audio files is a process ADPCM, MACE, for example. (4) The opposite of rarefaction whereby a quantity of data is reduced in order to occupy less storage space. See ATRAC.
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AM suppression : The ability of an FM tuner or receiver to reject amplitude modulation of the received signal and be sensitive only to frequency modulation. Much of the interference and noise in broadcasting appears as amplitude modulation, so a tuner with good AM suppression will have less distortion and noise than a tuner with poorer suppression. Also called AM rejection.

address track : A control/timing track on the edge of videotape (1", C, and 3/4" formats) that contains control data for quick and accurate location of program material, recorded at the same time as the picture. See control track.

brightness : The amount of high-frequency signal present in a sound, which tends to make the sound appear closer. The opposite of darkness.

bulk tuning message : A System-Exclusive message of the non-real-time type that allows the exchange of tuning data between MIDI devices as well as other devices such as computers, allowing microtuning or different temperaments by defining a specific pitch value. The frequency range is from 8.1758 Hz to 13,289.73Hz, in steps of one half-step cents, for each of the 128 notes in the MIDI range. Two messages are involved: a bulk tuning dump request message which is transmitted by a device in order to signify that it is ready to receive, and a bulk tuning dump message which contains the data for 128 tuning programs, each containing 128 pitch values.

channel message : A class of MIDI messages which only affect devices on a MIDI network set to a particular channel, i.e., all non-system messages. Channel messages may be of either Channel Mode or Channel Voice type. See MIDI.

channel pressure : A type of MIDI channel message that is applied equally to all of the notes on a given channel; the opposite of poly pressure, in which each MIDI note has its own pressure value. Also called aftertouch, channel pressure is generated on keyboard instruments by pressing down on a key or keys while they are resting on the keybed. Also called channel key pressure.

compression driver : A specialized mid- or high-frequency speaker consisting of a small diaphragm and voice coil coupled to a large magnet structure. The unit is mounted to a horn which acoustically matches the impedance of the driver to the impedance of the air and shapes the signal. Expensive due to the precise tolerances required, compression drivers are substantially more efficient than traditional direct-radiating cone speakers.

compression ratio : (1) The ratio of the dB change from input level to output level effected by a compressor, once the threshold has been exceeded. (2) In data compression, the ratio of the number of bytes of uncompressed to compressed data, an indication of the space-saving efficiency of the compression algorithm.

compressor/limiter : A device for reducing the effective dynamic range of an input signal by preventing it from rapidly exceeding or falling below a selected amplitude threshold. The first part of a compander, it is used to make loud parts of a signal softer and soft parts louder. Beyond the threshold, the ratio of the signalís input level to its output level (e.g., 2:1, 4:1) is user-selectable. A compressor is commonly used to keep mic levels within an acceptable range, but because it can slow a signalís rate of decay below the threshold, compressors are also used to add sustain to instruments such as electric guitar and bass. The limiter acts like a compressor, but operates only at the top end of the dynamic range. The limiter has a faster attack time (1Ķs to 1ms) than the compressor alone (1ms to 10ms). A compressor/limiter is inserted between the outputs of a MIDI soundcard, synthesizer, or mixer and the inputs of the mixdown deck. See hard knee compression, soft knee compression.

end-addressed : A microphone that is aimed at the sound source, as opposed to side-addressed, which is aimed with the side of the mic at the sound source.

equal loudness curves : Also known as Fletcher-Munson curves or phon lines. Equal loudness curves are the inverse of frequency response curves and reflect the phenomenon that humans do not hear all frequencies as having equal loudness. In other words, human hearing is not liner in frequency. This is particularly problematic in recording as a mixed master will be perceived differently depending on the playback level. Specifically, there is a marked drop-off in aural sensitivity at low frequencies. At the opposite extreme, humans have high sensitivity to sounds in the 1kHz-8kHz range, with sound again dropping away above 12kHz. Also called equal loudness contours. In the graph below, note that at 60dB SPL, a 1kHz tone is perceived as of equal loudness as a 20Hz tone at over 100dB SPL. At low levels, these differences are accentuated: the same 1kHz tone at 10dB SPL requires 80dB SPL at 20Hz.

ESS : Early Sound Scattering. A design for control rooms where the characteristic reflections are so uniformly random that they have no character to impose on the listening space. An ESS control room is one which features a highly diffusive front end (including the monitor walls) which scatters the early sound using Schroeder-type diffusers. The body of the room is absorbent, with most of the lows damped by membrane panels. These rooms can be made fairly live compared to older control rooms, with a flat frequency response and good stereo imaging, both of which remain stable right to the rear corners of the room. As compared with LEDE and RFZ designs.

expression : One of the defined MIDI Controller Change messages, usually assignable to some parameter in a synthesizer, such as Volume or Filter Cut Off.

hard knee compression : A characteristic of certain designs of a compressor wherein nothing happens to an input signal until the signal reaches the threshold limit, but as soon as it does, the full level of gain reduction is applied, as determined by the ratio control setting. A graph of the input gain against the output gain will show a sharp change in slope at the threshold level. Compare with soft knee compression."

high-frequency compression : See HX/HX pro.

key pressure : See poly pressure.

lossy/lossless : If, upon decoding by a codec, an audio file compression algorithm restores the sound to its original fidelity, it is said to be lossless. To the extent that the exact sound quality of the uncompressed signal cannot be reconstructed, the algorithm is said to be lossy.

loudness : Loudness is a subjective attribute of sound and cannot be quantified. If a large group of listeners is asked to adjust the strength of two signals so that one is twice as loud as the other, the average power difference will be about 10dB, and this will be almost independent of the absolute levels of the two sounds. The loudness of a sound, especially a complex sound containing many frequencies, has no simple relation to its SPL.

loudness control : An addition to some amplifiers or preamplifiers which attempt to correct for the reduced aural sensitivity to low-frequency, low-level sounds. The loudness control is simply a bass-boost circuit which has a relatively greater effect as the volume is turned down so that the perceived loudness of each frequency is the same as the loudness of a 1kHz tone.

Meridian Lossless Packing : See MLP.

MIDI message : A full instruction consisting of at least one status byte and frequently with one or more data bytes, which causes a MIDI device to perform one of the functions defined in the MIDI specification. See also entries for each message type.

mixdown session : A recording session during which the separate tracks of a multitrack tape are processed and combined or blended into two or more channels, then rerecorded onto a multitrack recorder. The resulting tape is called the master tape and is the finished studio product. The master is ready, at this stage, for dubbing.

multiband audio processor : A type of compressor, used by FM radio stations, which breaks up the audio frequency spectrum into from three to five bands, runs them through individual compression components, and then add them back together, resulting in a kind of re-equalization. This process tends to even out the bands, reducing the boominess of mixes with heavy bass, and the tinniness of mixes with a lot of high-frequency signal. See split-band compression.

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