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Entries found for search: Q

audio frequency : See AF.

analog sequencer : A sequencer into which sounds for storage and playback are fed as analog signals, via analog potentiometers.

active equalizer : An equalizer that employs active components such as transistors or ICs in its processing circuits. A pre-amplifying circuit generally follows each stage of actual equalization, boosting the signal level to restore unity gain. See also passive equalizer.

center frequency : The frequency that is boosted or attenuated most by the operation of any parametric equalizer or other similar processing device or circuit. See Q.

composite equalization : The overall frequency response modification produced when a signal passes through more than one equalizing circuit in the same device, or through several equalizers in a series.

corner frequency : See rolloff frequency.

critical frequency : See rolloff frequency.

crossover frequency : The frequency above and below which an audio signal is divided into two bands, each of which is directed to a separate destination. Precisely, the frequency at which each of the two bands is attenuated 3dB by the crossover network.

cutoff frequency : See rolloff frequency.

elliptical equalizer : A special equalizer which causes the two channels of a stereo signal to be more nearly in phase at low frequencies, making the signal easier to cut into a record (an LP stylus has an elliptical cross-section).

equalizer : An adjustable audio filter inserted in a circuit to divide and adjust its frequency response, altering or distorting the relative amplitude of certain frequency ranges of an audio signal. The effects processor used for equalization. Equalizers come in two varieties, graphic and parametric. A graphic equalizer typically has a number of fixed-frequency bands (5-10 in consumer equipment, 31 in professional equipment), each wired to its own front-panel slider. The control is over the amount of cut or boost (in dB) at each band. A parametric equalizer goes two steps further: the center frequency of each band can be selected by the user, as can the bandwidth. This affords more precise control over which frequencies will be affected by the boost or cut in amplitude. Because EQ circuitry with these controls is more expensive to build, a parametric equalizer will typically provide fewer bands than a graphic equalizer. A semi-parametric equalizer, sometimes found in multieffects devices, provides control over the center frequency of each band, but not over the bandwidth. See also active equalizer, passive equalizer, shelving equalizer, Q.

equalization (EQ) : An effect that allows the frequency-selective manipulation of a signal’s amplitude. The simplest equalizers are shelving types, offering the ability to cut or boost gain above or below a given frequency. Equalization doesn’t only change the level of specific parts of the audio spectrum, it also changes the phase of the affected frequencies relative to those that aren’t being EQ’d, i.e., EQ affects both the frequency response and phase relationships of the signal. See composite equalization, pre-emphasis, room equalization.

equalization curve : In tape recording and playback, a standardized equalization effect applied to an audio signal. Pre-emphasis and the complementary de-emphasis curve is applied to the recorded and reproduced signal, respectively. Pre- and post- equalization curves are different for each standard tape speed, and standards are given by the various organizations such as NAB, CCIR, and IES for their respective countries. Also described as a pre-emphasis curve and de-emphasis or post-emphasis curve. See also RIAA curve.

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.

equal-tempered : A system of tuning in which the diatonic comma is divided equally between the twelve half-steps of the octave. All the half-steps are equal in size and are exactly one-twelfth of an octave, spanning a frequency ratio of , or about 6%, or 1:1.059. In equal temperament, all the intervals are the same regardless of the key in which one is playing, and none except the octave is perfectly tuned. This makes it very easy to modulate from one key to another, although the keys lose their individuality because they all have equal intervals. The result is that the fourth and fifths are within 0.001% of just intervals, however the thirds are about 0.01% away from pure thirds which produce audible beats, the thirds in all keys being equally bad. See temperament, syntonic comma, diatonic comma.

equivalent input noise (EIN) : EIN is becomming a common method for specifying noise in audio equipment. This is a computed figure equal to the noise measued at some gain setting, minus the gain. For example, if a microphone preamplifier puts out -85dBV noise when set for 40dB of gain, the EIN is -125dBV. Note that, while -125dBV seems better than -85dBV, both figures represent the same amount of noise."

erase frequency : See erase head.

extinction frequency : In magnetic tape recording, the high frequency beyond which significant cancellation occurs because its wavelength on tape, at the specified tape speed, approaches the width of the head gap.

Sabine equation : The reverberation time of a room is found using the Sabine equation:

RT60 = 0.049 X (V/Sa)

reference frequency : See line-up tone.

graphic equalizer : A graphic equalizer can be recognized by the row of faders across the front panel, each fader controlling its own narrow section of the audio spectrum. Other than the highest and lowest faders, which control shelving filters, each of the filters in a graphic equalizer is a fixed-frequency bandpass filter, where the range of each fader is fixed, and the width of each individual band of a third-octave equalizer is actually wider than a third-octave. See equalizer, parametric equalizer.

frequency response errors : Any deviation from a linear output response in an audio device.

frequency : The number of waves (or cycles) arriving at or passing a point in one second, expressed in Hertz. See pitch, Appendix D.

frequency distortion : Frequency distortion results when the amplitude of the output of a system or a device varies as the frequency of the input varies, while the amplitude of the input is held constant.

frequency doubling : See doubling.

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