This paper presents the empirical relationships between various types of noises and the audio performances of various types of dithering systems based on extensive computer numerical simulations. There are two types of dithering systems. They are the subtractive dithering systems and the nonsubtractive dithering systems. For the subtractive dithering systems, artificial noises are added before and after the quantizer. For the nonsubtractive dithering systems, there is only a single artificial noise added before the quantizer. Also, there are two types of subtractive dithering systems. They are the synchronous subtractive dithering systems and the asynchronous subtractive dithering systems. The artificial noises added before and after the quantizer are the same for the synchronous subtractive dithering systems, while they are different for the asynchronous subtractive dithering systems. In this paper, both the subtractive dithering systems and the nonsubtractive dithering systems as well as both the synchronous subtractive dithering systems and the asynchronous subtractive dithering systems are studied. Besides, the Gaussian distributed noises, the uniform distributed noises and the bilaterial exponential distributed noises as well as the sinusoidal input signals are employed for evaluating both the signal to noise ratios (SNRs) and the tunal suppression ratios (TSRs). Computer numerical simulation results show that the synchronous subtractive dithering systems outperform the nonsubtractive dithering systems. Also, the use of the uniform distributed noises outperforms the use of the other two types of noises. Moreover, the asynchronous subtractive dithering systems achieve constant TSRs independent of both the type of the noises and the SNR levels.
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