Glossary definition of 'Cross-talk'

Undesirable leakage of a signal from one circuit or channel to another.

The main mechanisms for cross-talk are capacitive, inductive or conductive coupling between electronic circuits or channels. When recording with multiple microphones, leakage from one sound source into the microphone intended to record another source is also sometimes termed "cross-talk", in which case the mechanism is acoustic. Inter-channel cross-talk is sometimes referred to as channel separation.

Measuring cross-talk
Cross-talk is expressed as a ratio (usually dB) of the undesired signal in a channel to the level of a desired signal in another channel. To measure this, a signal is passed through one channel and its output level measured. Another channel into which we are measuring cross-talk is set up with its input terminated, but no signal present. The output of this channel is measured. The ratio of the output of the second channel to the level of the first channel is the cross-talk. This will be a negative number in dB since the level in the second channel will be lower than that in the first.

Note also that the level of cross-talk signal measured in the second channel is likely to be very low and could be dominated by noise. For this reason it is good practice to place a band-pass filter at the frequency being tested to reduce the effects of noise on the measurement. If there are controls which affect the gain on the two channels, they should be set identically if possible, and/or the conditions of the measurement stated.

Cross-talk mechanisms, in particular capacitive effects, are highly frequency dependent. It is therefore essential that the frequency at which the cross-talk is measured is stated, or a range of frequencies and a tolerance is given, for example:

Cross-talk: <120dB, 20Hz-20kHz; -130dB, 1kHz