An instrument that measures the amount of noise in a transmission system, particularly a telephone system. It includes a device for measuring noise power through a weighting network in order to produce objective results that approximately parallel subjective results with human observers. Standard psophometric weighting characteristics have been produced by the CCITT.

Crosstalk and other noise may be measured by passing a suitable noise signal down one telephone channel and measuring the amount of this noise that appears on an adjacent line with a psophometer with standard weighting characteristics.