One of the types of error introduced into an analog audio signal by encoding it in digital form. The digital equivalent of tape hiss, quantization noise is caused by the small differences between the actual amplitudes of the points being sampled and the bit depth of the analog to digital converter. In the quantization of a sine wave whose frequency is a submultiple of the sampling frequency, the error will have a definite pattern which repeats at the frequency of the signal, having a frequency content consisting of multiples of this frequency, where it can be considered as harmonic distortion rather than noise. In music, however, the signal is constantly changing and no such regularity exists, resulting in quantization error, producing wideband noise, called quantization noise. See granulation.