Effects of speech babble on transient evoked otoacoustic emissions in normal-hearing adults

The results of transient evoked otoacoustic emissions (TEOAEs) have been found to be adversely affected by noise. However, there are few investigations into the specific effect of background noise on TEOAEs. The purpose of the present study was to determine the effects of increasing levels of speech babble and the recording method on TEOAEs using the ILO88 Otodynamics instrumentation. Subjects were 30 normal-hearing adults (15 males and 15 females), aged between 18 and 32 years. TEOAE recordings were obtained from both ears of each subject under five different levels of speech babble delivered via a loudspeaker in sound field using both the default and Quickscreen methods of data collection. The results indicated that both the whole-wave reproducibility (WWR) and mean signal-to-noise ratio (MSNR), averaged across frequencies from about 2 to 4 kHz, decreased with increasing speech babble levels. The results also showed that the Quickscreen mode was less susceptible to noise than the default mode. The pass percentage, using either WWR > or = 50 percent or an MSNR > or = 3 dB as a pass criterion, also decreased with increasing speech babble levels. Furthermore, the findings indicated that the use of the WWR pass criterion resulted in a high failure rate under high levels of speech babble. In contrast, the MSNR pass criterion was robust to speech babble levels of up to 70 dBA in the Quickscreen mode and 65 dBA in the default setting. The clinical implications of these findings, as applied to non-sound-treated environments, are discussed.