Speech-in-noise intelligibility does not correlate with efferent olivocochlear reflex in humans with normal hearing

Abstract

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=20dB SPL. Average SRT was −6.66 dB (−4.50 to −7.65dB, SD 0.63dB). CS increased with decreasing primary tone levels, with mean absolute CS values in the range of 0.6–6dB SPL. Test–retest repeatability was good. Statistical evaluation revealed no significant relationship between SI and CS of DPOAE.

• Olivocochlear efferents
• medial olivocochlear reflex
• speech intelligibility
• discrimination
• background noise
• distortion product otoacoustic emissions