To evaluate the effect of contralateral acoustic stimuli on speech identification scores and to correlate this effect to contralateral suppression of evoked otoacoustic emission.
Ten normal-hearing children with good academic performance participated in the study. Speech identification scores were measured in quiet and with different ipsilateral signal to noise ratios in two conditions, with and without contralateral acoustic stimuli. Transient evoked otoacoustic emissions were recorded for 70 dB SPL clicks with and without contralateral acoustic stimuli.
Findings revealed that contralateral acoustic stimuli enhanced speech perception when ipsilateral signal to noise ratios was +10 dB and +15 dB. This enhancement had significant positive correlation with contralateral suppression of OAE.
The results of the present study support the hypothesis that medial olivocochlear bundle might aid in speech perception in noise, thereby suggesting a possible role of cochlear efferent fibers in hearing. The psychoacoustic measures can be used to evaluate the efferent auditory pathways, where it is not possible to record otoacoustic emissions.
This study was designed to assess the functional role of the olivocochlear bundle in noise. The functioning of the olivocochlear bundle was assessed both through psychoacoustical and physiological measures in 10 normal-hearing children. Contralateral suppression of otoacoustic emission was used as the physiological measure, and shift in speech identification scores on the contralateral acoustic stimuli was used as the psychoacoustic measure. Results revealed a significant positive correlation between these two techniques at lower ipsilateral signal-to-noise ratios. This supports the hypothesis that the olivocochlear bundle helps in speech understanding in noise.
Department of Audiology, All India Institute of Speech & Hearing, Mysore, India.
Received February 24, 2003; accepted November 12, 2003
Address for correspondence: Ajith Kumar, Lecturer in Audiology, All India Institute of Speech & Hearing, Manasagangothri, Mysore, 570006 Karnataka, India. E-mail: email@example.com.