Dependency of tonality perception on frequency, bandwidth, and duration

Abstract

Psychoacoustic studies show that a narrowband noise masker exhibits a stronger simultaneous masking effect than a tonal masker with the same signal power placed at the noise center frequency. Consequently, perceptual audio codecs commonly incorporate some sort of tonality estimation as part of their perceptual model. However, common tonality estimation techniques do not necessarily reflect the perception of tonality by human listeners. As long as the tone and narrowband noise signals are long enough, they are easily distinguishable for normal hearing listeners. However, if the stimulus duration decreases, both signal types approach the shape of impulses, and therefore, at some point become audibly identical. Consequently, at a given frequency and noise bandwidth, there is a duration threshold below which the signals cannot be distinguished. A series of so-called “2-AFC 3-step up-down” psychoacoustic tests are designed and carried out to investigate the frequency and bandwidth dependency of these duration thresholds. The test results, collected from 32 listeners, are statistically evaluated and confirm a decreasing threshold for increasing center frequency and bandwidth. These results can be used to improve psychoacoustic models for audio codecs by using tonality estimators with frequency and bandwidth adapted temporal resolution.