Adobe 65009626 User Guide - Page 95

USING SOUNDBOOTH CS4 91 Digital audio glossary compressor An effect that reduces dynamic range by lowering amplitude when an audio signal rises above a specified threshold. For example, a compressor can compensate for variations in level caused by a vocalist who occasionally moves away from a microphone. Or, during mastering, a compressor can produce consistent levels for full program material, providing a solid, professional sound for web, video, and radio presentations. (See "mastering" on page 92.) crossfade A fade from one audio track to another. D DAC (digital-to-analog converter) The hardware that converts a digital audio or video signal into an analog signal that you can play through amplifiers and speakers. DAT (digital audio tape) A standard two-track digital audio tape format. DAT tapes are sampled at 16 and 24 bits, and 32,000, 44,100, and 48,000 samples per second. (The latter is often described as DAT quality.) DAW (digital audio workstation) A computer system used to edit, process, or mix audio. dBFS Decibels below full scale in digital audio. The maximum possible amplitude is 0 dBFS; all amplitudes below that are expressed as negative numbers. A given dBFS value does not directly correspond to the original sound pressure level measured in acoustic dB. DC offset Some sound cards record with a slight DC offset, in which direct current is introduced into the signal, causing the center of the waveform to be offset from the zero point (the center line in the waveform display). DC offset can cause a click or pop at the beginning and end of a file. decibel (dB) In audio, the decibel (dB) is a logarithmic unit of measurement used for amplitude. delay A time-shifted signal that you can mix with the original, nondelayed signal to provide a fuller sound or create echo effects. dithering Adds small amounts of noise to a digital signal so that very quiet audio remains audible when you convert from a high-bit resolution to a lower one (for example, when converting from 32-bit to 16-bit). Without dithering, quiet audio passages such as long reverb tails may be abruptly truncated. dry Describes an audio signal without any signal processing such as reverb; the opposite of wet. DSP (digital signal processing) The process of transforming a digital audio signal by using complex algorithms. Examples include filtering with equalizers, and effects processing with reverbs and delays. DVD A storage medium similar to a CD, but with much higher bandwidth and storage capabilities. Audio in DVD movies generally uses a 96-kHz sample rate and a 24-bit depth. dynamic range Audio amplitude range, from quietest troughs to loudest peaks. (See also "bit depth" on page 90 and "decibel (dB)" on page 91.) E equalization (EQ) The process of increasing or decreasing the amplitude of specific audio frequencies relative to the amplitude of other audio frequencies. expander Increases dynamic range by lowering amplitude when an audio signal falls below a specified threshold (the opposite of a compressor). For example, an expander can be used to lower the level of background noise that becomes audible when a musician stops playing. Updated 15 July 2009