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Updated: Jul 11, 2026

Morphological and Functional Evaluation of Ribbon Synapses at Specific Frequency Regions of the Mouse Cochlea
Published on: May 10, 2019
Speech-in-noise intelligibility does not correlate with efferent olivocochlear reflex in humans with normal hearing
Wolfgang Wagner1, Kathrin Frey, Guido Heppelmann
1Tübingen Hearing Research Center, Department of Otolaryngology/Head and Neck Surgery, University of Tübingen, Germany. w.wagner@med.uni-tuebingen.de
Conclusion:
According to the presented data, speech-in-noise intelligibility (SI) does not correlate with olivocochlear efferent activity - as measured by contralateral suppression (CS) of distortion product otoacoustic emissions (DPOAE) in humans with normal auditory threshold.
Objectives:
Literature data indicate a possible role of the medial olivocochlear efferents in speech intelligibility, especially in background noise. The objective of this study was to investigate this relationship.
Materials And Methods:
SI was evaluated in three independent sessions by determining the ratio speech level/noise level, at which 50% of the words are understood (i.e. speech reception threshold, SRT). Efferent activity was inferred measuring CS of DPOAE, using two different paradigms with extensive variation of stimulus parameters and duplicate measurements.
Results:
For optimum measurement of CS, the study was restricted to subjects (n =49) with valid DPOAE down to primary tone levels L1=47/L2 =20 dB SPL. Average SRT was -6.66 dB (-4.50 to -7.65 dB, SD 0.63 dB). CS increased with decreasing primary tone levels, with mean absolute CS values in the range of 0.6-6 dB SPL. Test-retest repeatability was good. Statistical evaluation revealed no significant relationship between SI and CS of DPOAE.
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