| Autor: |
Tandetnik, S., Gamier, S., Lorenzi, C. |
| Zdroj: |
British Journal of Audiology; December 2001, Vol. 35 Issue: 6 p355-364, 10p |
| Abstrakt: |
AbstractFirst- and second-order modulation detection thresholds were measured in normal hearing and hearing-impaired listeners. ‘First-order’ modulation detection thresholds correspond to the ability of listeners to detect sinusoidal amplitude modulation (SAM); they are measured as a function of the frequency of that modulation, fm. ‘Second-order’ modulation detection thresholds correspond to the ability to detect sinusoidal modulation applied to the modulation depth of a SAM signal; they are measured as a function of the frequency of the modulation applied to the modulation depth (referred to as/ fm1). In this case, the SAM signal acts as a ‘carrier’ stimulus of frequency fmand sinusoidal modulation of the SAM-signal’s modulation depth (at rate fm1) generates two additional components in the modulation spectrum at fm − fm1and fm + fm1. In both groups of listeners, first-order modulation detection thresholds were measured for modulation frequencies fmranging between 4 Hz and 32 Hz, and second-order modulation detection thresholds were measured for second-order modulation frequencies fm1ranging between 1 Hz and 11 Hz, using a fixed first-order modulation frequency fmof 16 Hz. The results showed that, in hearing-impaired listeners: first-order modulation detection thresholds were within the normal range up to fm= 16 Hz and poorer than normal at fm1= 32 Hz; second-order modulation detection thresholds were within the normal range at fm1= 3, 5 and 11 Hz, and poorer than normal at fm1= 1 Hz and 7 Hz. These results suggest that cochlear damage has little effect on the detection of both sinusoidal and complex temporal envelopes. |
| Databáze: |
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