Perceptual Differences for Harmonic Complex Signals Related to Dispersion in the Inner Ear
In this paper we investigate the importance of the filter process in the inner ear for the perception of harmonic complex signals. To study the (amplitude) attenuation of the internal filter and, in addition, the phase and group delay characteristic, we use harmonic complex signals with constant amplitude spectra and constant temporal envelopes. The phase angles of the harmonic components are chosen in such a manner that the instantaneous frequency is linearly sweeping up or down within each period of the complex. Because of the phase-dispersive properties of the basilar membrane, up and down sweeps lead to different waveforms in the inner ear. For reasons of comparison, a periodic pulse sequence, built up of the same harmonics in sine phase, is included in the experiments. These complex tones are used to mask a short sinusoid presented at different parts of the masker's period. The resulting pattern of masked thresholds fits well with model calculations performed with a digitally realized basilar membrance model. The results reveal that peripheral preprocessing influences the perception of complex signals not only through a frequency-specific attenuation, but also through a frequency-specific phase delay.
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