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A manufacturer of audio processing equipment, most notably compressors and tape noise reduction systems. The DBX NR systems were commercial encode/decode analogue noise-reduction processors intended for consumer and semi-pro tape recording. Different models varied in complexity, but essentially DBX compressed the audio signals during recording and expanded them by an identical amount on playback.

A means of representing information (eg audio or video signals) in the form of binary codes comprising strings of 1s and 0s, or their electrical or physical equivalents. Digital audio circuitry uses discrete voltages or currents to represent the audio signal at specific moments in time (samples). A properly engineered digital system has infinite resolution, the same as an analogue system, but the audio bandwidth is restricted by the sample rate, and the signal-noise ratio (or dynamic range) is restricted by the word-length. (cf. Analogue)

Direct Memory Access. Part of a computer operating system that allows peripheral devices to communicate directly with the computer memory without going via the central processor (CPU).

A type of microphone that works on the electric generator principle, such as Moving Coil and Ribbon mics. An acoustical sound wave impacts the microphone diaphragm which then moves an electrical conductor within a magnetic field to generate a current, the amplitude and polarity of which reflects the acoustic signal.

A device which allows the user to adjust the tonality of a sound source by boosting or attenuating specific ranges of frequencies. Equalisers are available in the form of shelf equalisers, parametric equalisers and graphic equalisers — or as a combination of these basic forms. (cf Filter)

An electronic circuit designed to attenuate a specific range of frequencies. (See low-pass, high-pass and band-pass.) The amount of attenuation depends on the filter slope which is typically either 6, 12, 18 or 24dB/Octave. 

The standard measurement of frequency. 10Hz means ten complete cycles of a repeating waveform per second. (Previously defined as 'cycles per second or CPS).

The ‘resistance’ or opposition of a medium to a change of state, often encountered in the context of electrical connections (and the way signals of different frequencies are treated), or acoustic treatment (denoting the resistance it presents to air flow). Although measured in Ohms, the impedance of a ‘reactive’ device such as a loudspeaker drive unit will usually vary with signal frequency and will be higher than the resistance when measured with a static DC voltage.

Signal sources have an output impedance and destinations have an input impedance. In analogue audio systems the usually arrangement is to source from a very low impedance and feed a destination of a much higher (typically 10 times) impedance. This is called a ‘voltage matching’ interface. In digital and video systems it is more normal to find ‘matched impedance’ interfacing where the source, destination and cable all have the same impedance (eg. 75 Ohms in the case of S/PDIF).

Microphones have a very low impedance (150 Ohms or so) while microphone preamps provide an input impedance of 1,500 Ohms or more. Line inputs typically have an impedance of 10,000 Ohms and DI boxes may provide an input impedance of as much as 1,000,000 Ohms to suit the relatively high output impedance of typical guitar pickups.

A separate room or enclosure, often called a 'Booth' designed to provide acoustic isolation from external noise. Often used alongside a studio's main live room to record vocals or drums, for example, without spill from other instruments.