Monaural and binaural frequency selectivity in hearing-impaired subjects

Abstract

Abstract

Sensorineurally hearing-impaired (HI) subjects often report difficulties in complex acoustical environments. To investigate whether these problems arise from specific deficits in the frequency selectivity in binaural listening conditions, thresholds were measured for a 500-Hz sinusoid in phase (So) or antiphase (Sπ) masked by a diotic notched noise (No). The equivalent rectangular bandwidth (ERB) for filters derived from diotic (NoSo) and dichotic (NoSπ) threshold curves is larger for the HI subjects than for the normal-hearing (NH) subjects. However, the ratio of binaural to monaural ERB is the same. The data indicate that there is no additional retrocochlear impairment reducing the binaural frequency selectivity of HI subjects. A specific binaural impairment was also tested by measuring the perception of binaural pitch (Huggins’ pitch). Two out of eight HI subjects failed to perceive this pitch, although in the masking experiment they obtained a binaural masking-level difference of up to 10 dB. The current data therefore provide no clear evidence for a specific binaural impairment factor in hearing impairment that deteriorates several aspects of binaural processing in a similar way.

Sumario

Los sujetos con hipoacusia sensorineural (HI) a menudo reportan dificultades cuando se encuentran en ambientes acústicos complejos. Para investigar si estos problemas surgen por deficiencias específicas en la selectividad de frecuencias en condiciones de audición binaural, se midieron los umbrales para sinusoides de 500Hz en fase (So) o en antifase (Sω) enmascarados con un ruido con muesca diótica (No). La banda ancha rectangular equivalente (ERB) para filtros derivaba de curvas umbral dióticas (NoSo) y dicóticas (NoSω) son más amplias para los sujetos con HI que para los sujetos normoyentes (NH). Sin embargo, el ratio de ERB binaural / monoaural es la misma. Los datos indican que no hay un impedimento retrococlear adicional cuando se reduce la selectividad binaural de frecuencias en los sujetos con HI. También se hizo una prueba de impedimento binaural específico por medio de la medición de la percepción binaural de tono (Huggins’ pitch). Dos de cada ocho sujetos no pudieron percibir este tono, aunque en el experimento con enmascaramiento, obtuvieron un nivel binaural de diferencia de enmascaramiento de hasta 10dB. Estos datos no dan una evidencia clara de un impedimento binaural específico en la hipoacusia que deteriore diversos aspectos del procesamiento binaural en una forma similar.

Key Words:

• Hearing impairment
• Frequency selectivity
• Binaural perception
• Binaural masking-level difference
• Huggins’ pitch
• Across-frequency processing
• Masking

Acknowledgements

Parts of this study have been presented at the ‘35. Erlanger Kolloquium’ in Erlangen, Germany (Nitschmann, 2008a); at the ‘11. Jahrestagung der Deutschen Gesellschaft für Audiologie’ in Kiel, Germany (Nitschmann et al, 2008b); and at the joint ASA-EAA conference in Paris, France (Nitschmann et al, 2008c). This study was supported by the Deutsche Forschungsgemeinschaft (DFG GRK 591/3 and SFB tr31), the HearCom project, and the Audiologie-Initiative Niedersachsen.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.