Equivalent pulse code modulation noise

In telecommunications, equivalent pulse code modulation (PCM) noise is the amount of noise power on a frequency-division multiplexing (FDM) or wire communication channel necessary to approximate the same judgment of speech quality created by quantization noise in a PCM channel. Note 1: The speech quality judgment is based on comparative tests.

Source: Wikipedia — Equivalent pulse code modulation noise (CC BY-SA 4.0)