RESUMEN
To investigate the effect of acoustic reflex decay sounds on the amplitude of distortion product otoacoustic emission in adults with normal hearing threshold level. A total of 20 subjects of both sexes aged between 18 and 25 years [mean: 22 years] were examined. Inclusion criteria were normal otoscopic and tympanoscopic findings, and pure tone thresholds of <20dB for 500-2000 Hz frequency range. One ear of the subjects, i.e. 20 ears, underwent DPOAE recording followed by acoustic reflex and reflex decay testing for 500-2000Hz at the audiology department at King Hussein Medical Centre between September 2013 and August 2014. The study was approved by the Royal Medical Services ethical committee. All subjects were not paid or otherwise reimbursed. Significant difference in the mean distortion product otoacoustic emission amplitudes were noticed before and after acoustic reflex decay testing. The maximum DPOAE reduction of approximately 12 dB in the frequency range 750-2000 Hz after exposure to continuous steady high sound for 10 seconds. The distortion otoacoustic emission strength went back to base line before exposure after 30 minutes. There is a strong correlation between high continuous intensity sound and the reduction in the distortion product otoacoustic emission amplitude. The function of the outer hair cells [OHCs] is impaired after exposure to high intensity. Distortion product otoacoustic emissions [DPOAEs] are useful in examination of noise-induced level shifts, reflex decay high intensity sounds may result in temporary reduction in the distortion product otoacoustic emission strength. Further investigation to be carried out on a group of hearing impaired patients to quantify the effect of the acoustic reflex decay on the distortion product otoacoustic emission amplitude whether its the OAE amplitude reduction is temporary or permanent