Perceptual (ir)relevance of HRTF magnitude and phase spectra
This paper discusses the perceptual consequences of smoothing of anechoic HRTF phase and magnitude spectra. The smoothing process is based on a binaural perception model, in which interaural cues in the auditory system are rendered at a limited spectral resolution. This limited resolution is the result of the filterbank present in the peripheral auditory system (i.e., the cochlea). Listening tests with single and multiple virtual sound sources revealed that both the phase and magnitude spectra of HRTFs can be smoothed with a gammatone filter which equals estimates of the spectral resolution of the cochlea without audible artifacts. The amount of smoothing was then increased by decreasing the order of the gammatone filters. If the filter order is reduced by a factor 3, subjects indicate spectral and positional changes in the virtual sound sources. The binaural detection model developed by Breebaart, van de Par and Kohlrausch was used to predict the audibility of the smoothing process. A comparison between model predictions and experimental data showed that the threshold at which subjects start to hear smoothing artifacts can be predicted accurately. Moreover, a high correlation exists between the model output and the amount of stimulus degradation reported by subjects.
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