Perceptual audio coders exploit the masking properties of the human auditory system to reduce the data rate of the input audio signal. Commonly, the input signal is split into frames and decomposed into a number of subbands, such that it is divided into time-frequency segments. A psychoacoustic model (PM) is used to estimate the masking threshold evoked by the audio signal as a measure for the maximum inaudible quantization noise. Thus, it enables a perceptually suitable bit allocation for the time-frequency segments. The effectiveness of the masking depends on whether the audio signal is tone-like or noise-like. This property is often referred to as ''tonality.'' Generally, tone-like sounds with no or slow envelope fluctuations and/or very regular envelope fluctuations are less effective maskers than noise-like sounds with strong, irregular, and more rapid envelope fluctuations. Perceptual audio encoders model this ''asymmetry of masking'' by means of tonality estimation methods. Further, the effectiveness of the input signal in masking the quantization noise is likely to depend on the bandwidth and center frequency of the audio signal, but the exact dependency of the masked threshold on the masker's bandwidth and center frequency had not previously been measured. The effect of bandwidth had been investigated in a few studies, however, only at medium center frequencies. A new psychoacoustic experiment was carried out to investigate masking when the noise masker had a narrower bandwidth than the noise probe, which is the most relevant case in perceptual audio coding. Statistical analysis of the data showed that the masked thresholds increased with increasing masker bandwidth and were lowest for medium center frequencies. Another effective parameter is the duration of the stimulus. Both perceptually and physically, a certain amount of time is needed to identify the tonality or noisiness of a sound. Hence, to exploit the fact that quantization noise is masked more effectively by a noise-like signal than by a ...
Psychoacoustics of detection of tonality and asymmetry of masking: implementation of tonality estimation methods in a psychoacoustic model for perceptual audio coding ; Psychoakustik der Tonalitätswahrnehmung und der Maskierungsasymmetrie: Implementierung von Tonalitätsschätzverfahren in einem psychoakustischen Modell für die wahrnehmungsbasierte Audiocodierung
2016-01-01
Theses
Electronic Resource
English
DDC: | 629 |
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