Abstract
Temporal information in a signal can be partitioned into temporal envelope (E) and fine structure (FS). Fine structure is important for lexical tone perception for normal-hearing (NH) listeners, and listeners with sensorineural hearing loss (SNHL) have an impaired ability to use FS in lexical tone perception due to the reduced frequency resolution. The present study was aimed to assess which of the acoustic aspects (E or FS) played a more important role in lexical tone perception in subjects with auditory neuropathy spectrum disorder (ANSD) and to determine whether it was the deficit in temporal resolution or frequency resolution that might lead to more detrimental effects on FS processing in pitch perception. Fifty-eight native Mandarin Chinese-speaking subjects (27 with ANSD, 16 with SNHL, and 15 with NH) were assessed for (1) their ability to recognize lexical tones using acoustic E or FS cues with the “auditory chimera” technique, (2) temporal resolution as measured with temporal gap detection (TGD) threshold, and (3) frequency resolution as measured with the Q10dB values of the psychophysical tuning curves. Overall, 26.5%, 60.2%, and 92.1% of lexical tone responses were consistent with FS cues for tone perception for listeners with ANSD, SNHL, and NH, respectively. The mean TGD threshold was significantly higher for listeners with ANSD (11.9 ms) than for SNHL (4.0 ms; p < 0.001) and NH (3.9 ms; p < 0.001) listeners, with no significant difference between SNHL and NH listeners. In contrast, the mean Q10dB for listeners with SNHL (1.8±0.4) was significantly lower than that for ANSD (3.5±1.0; p < 0.001) and NH (3.4±0.9; p < 0.001) listeners, with no significant difference between ANSD and NH listeners. These results suggest that reduced temporal resolution, as opposed to reduced frequency selectivity, in ANSD subjects leads to greater degradation of FS processing for pitch perception.
Highlights
Temporal information in a signal can be partitioned into temporal envelope (E) and fine structure (FS), based on the Hilbert transform, with E defined as amplitude contour of the signal and FS defined as the instantaneous phase information in the signals related to harmonic resolvability [1]
The present study has demonstrated that listeners with auditory neuropathy spectrum disorder (ANSD) have deficits in using the FS cues for lexical tone perception, with on average only 26.5% of tone responses being consistent with FS, compared to 60.2% of tone responses being based on FS for listeners with sensorineural hearing loss (SNHL) and 92.1% for listeners with NH
The present study examined the temporal resolution using a gap detection task in listeners with NH, with SNHL, and with ANSD
Summary
Temporal information in a signal can be partitioned into temporal envelope (E) and fine structure (FS), based on the Hilbert transform, with E defined as amplitude contour of the signal and FS defined as the instantaneous phase information in the signals related to harmonic resolvability [1]. Smith et al [2] constructed a set of acoustic stimuli, called “auditory chimera”, each having the envelope of one sound and the fine structure of another. This technique provides a way to study the relative importance of E and FS in speech and pitch perception. Wang et al used the “auditory chimera” technique to demonstrate that as hearing loss of listeners with sensorineural hearing loss (SNHL) becomes more severe, lexical tone recognition relies increasingly on E rather than FS cues, indicating that a degradation of the ability to process FS cues as a function of hearing impairment [8]. It is possible that reduced frequency selectivity may underlie the impaired ability to process FS information in aforementioned studies [15]
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