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(Nearfield) The acoustic zone close to a sound source or microphone. Often used to describe a loudspeaker system designed to be used close to the listener – although some people prefer the term 'close field'. The advantage is that the listener hears more of the direct sound from the speakers and less of the reflected sound from the room.
A means of arranging two or more directional microphone capsules such that they receive sound waves from the directions or interest at slightly different times due to their physical spacing. Information about the directions of sound sources is captured in the form of both level differences between the capsule outputs, generated by aiming directional polar patterns in different directions, and the timing differences caused by their physical spacing. Specific forms of near-coincident microphones include the ORTF and NOS arrangements.
The noise floor defines the amplitude of the sum of all noise sources and other unwanted signals within a system. This could be the ambient acoustic noise in a room, or the electrical noise in a recording system or other audio equipment. In a high quality audio system the noise floor is typically around -100dBu or better. The total dynamic range capability of a system is normally defined as the difference in amplitude between the noise floor and the highest signal that can be passed without distortion.
A system for reducing analogue tape noise or for reducing the level of hiss present in a recording. (See DBX and Dolby).
A system using spectrally-shaped dither to improve the perceived signal-to-noise performance of a digital audio system.
A term which describes digital recording systems that allow any parts of the recording to be played back in any order with no gaps. Conventional tape is referred to as linear, because the material can only play back in the order in which it was recorded.
A socket is said to be normalised when it is wired such that the original signal path is maintained unless a plug is inserted into the socket. The most common examples of normalised connectors are the insert points on a mixing console.
A specific form of near-coincident microphone array devised by the Nederlandse Omroep Stichting (NOS), the Dutch national broadcaster. The technique employs a pair of small-diaphragm cardioid microphones mounted with a mutual angle of 90 degrees and spaced apart by 30cm. The theoretical stereo recording angle is 81°.
A filter which only removes a very narrow band of frequencies, or even a single frequency in extreme cases. A notch filter has an extremely high Q value (narrow bandwidth).
An addition to the basic MIDI spec that allows Controllers 98 and 99 to be used to control non-standard parameters relating to particular models of synthesizer. This is an alternative to using System Exclusive data to achieve the same ends, though NRPNs tend to be used mostly by Yamaha and Roland instruments.
A slotted plastic or bone (or metal) component at the headstock end of a guitar neck used to guide the strings over the fingerboard, and to space the strings above the frets.
The rule which states that a digital sampling system must have a sample rate at least twice as high as that of the highest audio frequency being sampled, in order to avoid aliasing and thus reproduce the wanted audio perfectly. Because anti-aliasing filters aren't perfect, the sampling frequency has usually to be made slightly more than twice that of the maximum input frequency - which is why the standard audio rate of 44.1kHz was chosen for a nominally 20kHz audio bandwidth.