An aliasing type of distortion in digital audio systems due to the uncertainty in the level of the samples is known as granulation, also called quantization distortion. If the sampling rate is an exact multiple of the input tone frequency, granulation results in harmonic distortion, i.e., the distortion components are at multiples of the input frequency. If not, the granulation resembles random noise, in which case it may properly be called quantization noise.
See modulation noise.