Glossary 295
MSB (Most Significant Byte)—The byte of a digital word that represents the highest value. Contrast with LSB
Noise gate—An electronic switch that opens if the trigger signal falls below a speci- fied threshold and closes if the trigger signal exceeds the threshold. Typically used to shut off unwanted hiss and noise.
Nominal level—SeeOperating Level.
Nyquist theorem—The Nyquist theorem states that the sampling rate of a digital audio system must be at least twice that of the highest audio frequency, otherwise waveform distortion know as aliasing will occur. See also Aliasing.
OMNI—The MIDI mode in which a device responds to MIDI data on all 16 channels.
Operating level—This is the signal level at which a piece of audio equipment is designed to operate. The two most common operating levels are –10 dBV (316 mV), which is used by semiprofessional equipment, and +4 dBu (1.23 V), which is used by professional equipment.
Oversampling—Sampling an audio signal at a rate higher than the actual sampling rate to reduce noise caused by quantization errors.
PAM (Pulse Amplitude Modulation)—In the first part of the A/D conversion process, pulses occurring at the sampling rate are modulated by an analog audio signal. See also PCM.
PC—Originally, the abbreviation for personal computer. Although today it’s used as the generic name for any IBM-compatible personal computer, usually running a version of the Microsoft Windows operating system.
PCM (Pulse Code Modulation)—In the second part of the A/D conversion pro- cess, the pulses derived using PAM are converted into binary data words using PCM. See also PAM.
Peaking—A type of EQ circuit used to cut and boost a band of frequencies, producing a mountain-peak type response. The width of the band is called the Q. Midband EQ is usually of the peaking type. Compare with Shelving.
PEQ—An abbreviation for parametric EQ.
PFL (Pre Fader Listen)—Monitoring signals before the channel fader. Contrast with AFL.
Phantom powering—The technique for supplying condenser-type microphones a DC voltage via the signal carrying conductors of a balanced cable.
Pink noise—A type of random noise that contains an equal amount of energy per octave. For example, the bands 100–200, 800–1600, and 3000–6000 all contain the same amount of energy. White noise, on the other hand, has an equal amount of energy per frequency band. That is, 100–200, 800–900, and 3000–3100.
Post fader—The point in the signal path after the fader. Aux sends are often config- ured as post-fader sends, which means the aux send signal is sourced after the channel fader. The advantage of this is that the aux send signal can be controlled at the same time as the main channel signal using the same fader. Post-fader aux sends are typically used to feed effects processors. See also AFL.
Pre fader—The point in the signal path before the fader. Aux sends are often config- ured as pre-fader sends, which means the aux send signal is sourced before the channel fader. The advantage of this is that the aux send signal can be controlled independently of the main channel signal. Pre-fader aux sends are often used for foldback mixes. See also PFL.
Program Change—A type of MIDI message for selecting programs.
