RESUMEN
The role of auditory efferent feedback from the medial olivocochlear system (MOCS) and the middle-ear-muscle (MEM) reflex in tonal detection tasks for humans in the presence of noise is not clearly understood. Past studies have yielded inconsistent results on the relationship between efferent feedback and tonal detection thresholds. This study attempts to address this inconsistency. Fifteen human subjects with normal hearing participated in an experiment where they were asked to identify an alarm signal in the presence of 80 dBA background (pink) noise. Masked detection thresholds were estimated using the method of two-interval forced choice (2IFC). Contralateral suppression of transient-evoked otoacoustic emissions (TEOAEs) was measured to estimate the strength of auditory efferent feedback. Subsequent correlation analysis revealed that the contralateral suppression of TEOAEs was significantly negatively correlated (râ¯=â¯-0.526, nâ¯=â¯15, pâ¯=â¯0.0438) with alarm-in-noise (AIN) detection thresholds under negative signal-to-noise conditions. The result implies that the stronger the auditory efferent feedback, the worse the detection thresholds and thus the poorer the tonal detection performance in the presence of loud noise.
Asunto(s)
Estimulación Acústica/métodos , Vías Auditivas/fisiología , Umbral Auditivo , Cóclea/fisiología , Ruido/efectos adversos , Núcleo Olivar/fisiología , Enmascaramiento Perceptual , Percepción de la Altura Tonal , Reflejo Acústico , Detección de Señal Psicológica , Estapedio/inervación , Vías Eferentes/fisiología , Femenino , Humanos , Masculino , Factores de TiempoRESUMEN
The amplification outcomes of two hearing aid prescriptions, NAL-NL1 and Digital Perception Processing (DPP), of nine moderate to moderately severe hearing-impaired adults were compared in the same digital hearing instrument. NAL-NL1 aims at optimizing speech intelligibility while amplifying the speech signal to a normal overall loudness level (Dillon, 1999). DPP focuses on restoring loudness based on normal and impaired cochlear excitation models (Launer and Moore, 2003). In this comparison, DPP resulted in better sentence recognition performance than the NAL-NL1 algorithm in the signal-front/noise-side condition, and the two prescriptions gave similar performance in the signal-front/noise-front condition. Subjective evaluations by the participants using the Abbreviated Profile for Hearing Aid Benefit and sound quality comparisons did not give conclusive results between the two prescriptions. With each hearing aid prescription, the ability of the hearing aid circuitry to reduce the effects of noise was evaluated by a sentence-in-noise test in three conditions: (1) adaptive directional microphone (DAZ), (2) multichannel noise reduction system (FNC), and (3) a combination of FNC and DAZ (FNC + DAZ). In the signal-front/noise-side condition, DAZ and FNC + DAZ gave better performance than FNC in nearly all participants, whereas in the signal-front and noise-front evaluation, the conditions revealed no significant differences.