This paper investigates the subjective effects of the use of dither in digital audio systems. A short introduction to dithered and undithered quantization is given, and the subjective experiment is described. The results of listening tests on undithered, subtractive dithered and non-subtractive dithered quantization are presented. The listening tests were made with 4 to 12 bits/sample. The subjective tests show that subtractive dithering is preferred to undithered quantization up to 8 bits/sample. Nonsubtractive dithering was, with music stimuli, only preferred to undithered quantization at 4 bits/sample. With speech, nonsubtractive dither was preferred to undithered quantization up to 8 bits/sample. Triangular probability density function dither was only preferred to rectangular probability density function dither at very low bit rates.
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