A common complaint of children with auditory processing disorders (APD) is difficulty in understanding speech in the presence of background noise. Evidence from animal and human studies has suggested that the medial olivocochlear bundle (MOCB) may play a role in hearing in noise. The MOCB function can be evaluated by the suppression effect of the transient evoked otoacoustic emissions (TEOAE) in response to contralateral acoustic stimulation (CAS). The present study was conducted to investigate the suppression effect of TEOAE in APD children. The study groups comprised 15 APD children aged 8–13 years associated with learning disabilities and 15 controls matched for gender and age. The suppression effect of TEOAE was evaluated by comparing the TEOAE levels with and without CAS. A significantly reduced suppression effect of TEOAE was demonstrated in the APD group, when compared to the controls. In addition, higher TEOAE levels were found in the APD group, suggesting inherent reduced MOCB activity on the outer hair cells in APD children. These results imply that some APD children present low activity of the MOCB system, which may indicate a reduced auditory inhibitory function and affect their ability to hear in the presence of background noise.

Three different central auditory skills were compared and evaluated in 56 blind and 40 sighted subjects. The study consisted of three experiments conducted in three subgroups. Experiment A was performed in order to evaluate the localization function; experiment B for the temporal auditory resolution ability of the blind adult, and experiment C to test the ability of the blind person to discriminate speech material in noise. In all three experiments the blind subjects obtained significantly better results than the sighted subjects. From these results it was concluded that there is supporting evidence of a certain superiority of the blind individual with regard to central auditory function.

This study was designed to characterize the effect of background noise on the identification of syllables using behavioral and electrophysiological measures. Twenty normal-hearing adults (18-30 years) performed an identification task in a two-alternative forced-choice paradigm. Stimuli consisted of naturally produced syllables [da] and [ga] embedded in white noise. The noise was initiated 1000 ms before the onset of the speech stimuli in order to separate the auditory event related potentials (AERP) response to noise onset from that to the speech. Syllables were presented in quiet and in five SNRs: +15, +3, 0, -3, and -6 dB. Results show that (1) performance accuracy, d', and reaction time were affected by the noise, more so for reaction time; (2) both N1 and P3 latency were prolonged as noise levels increased, more so for P3; (3) [ga] was better identified than [da], in all noise conditions; and (4) P3 latency was longer for [da] than for [ga] for SNR 0 through -6 dB, while N1 latency was longer for [ga] than for [da] in most listening conditions. In conclusion, the unique stimuli structure utilized in this study demonstrated the effects of noise on speech recognition at both the physical and the perceptual processing levels.