Wannamaker, R.A. "Dither and Noise-Shaping in Audio Applications," M.Sc. Thesis, Dept. of Physics, Univ. of Waterloo, Waterloo, ON, 1990 Dec.



A detailed study is presented of problems associated with quantization in digital audio. Techniques for their amelioration are examined which fall into two major categories: dithering and noise shaping.

Dithering is examined as a means of eliminating quantization distortion and noise modulation. The development and theory of dither in audio is reviewed in detail for the first time. Required properties for dither signals are established and practical methods for generating appropriate dithers are presented. The suitability of such dither signals for audio applications is confirmed by means of psycho-acoustic testing with a variety of signals.

Noise shaping is investigated as a technique for reducing the perceived level of quantization noise in digital systems. Theoretical background is surveyed with an eye to developing practical design methodologies for audio applications. To this end, a new parametrization of the ISO 15-phon equal loudness data is presented for use in the design of noise shaping filters. Appropriate filter design techniques are developed and are used to generate a variety of noise shapers. Some potential problems with the noise shaping technique are treated.