Background: Military personnel are usually exposed to high levels of impulse noise (IN) which can lead to hearing loss.Objectives: The purpose of this study was to assess the effects of relatively low level exposure of impulse noise (IN) during shooting practice on hearing using pure tone audiometry (PTA) and transiently evoked otoacoustic emission (TEOAE) in military personnel.Materials and Methods: Forty male soldiers (mean age 20.08 years) were recruited for the study. Prior to their first shooting practice, PTA and TEOAE were recorded. After 15 minutes and one week post- practice PTA and TEOAE were compared.Results: Immediately after shooting practice significant differences in PTA at 500, 1000, and 4000 Hz were observed for the right ear and no significant difference at any frequency for the left ear. There was a significant difference in the amplitude of TEOAE 15 minutes after shooting practice at 500, 1000, 2000, 3000, and 4000 Hz in the right ear, while for the left ear the difference was significant at 1000 and 2000 Hz. One week after exposure a significant difference at 500 and 4000 Hz was found only in the right ear and a significant difference in the amplitude of TEOAE was observed at 500, 1000, 2000, 3000, and 4000 Hz.Conclusions: Even exposure lower than permissible levels may lead to acoustic trauma.TEOAE is more sensitive than PTA in detecting early hearing loss after military shooting exercises. Hearing protection equipment and appropriate surveillance programs are recommended.

Auditory Neuropathy Spectrum Disorders (ANSD) are new classification which was proposed in 2008 by Colorado Children’s Hospital Group and defined as normal otoacoustic emissions and absent ABRs in newborn. In our long term follow up study, hearing of ANSD are changed into three types. Type I is normal OAE and normal ABR (normal hearing), Type II is absent OAE and absent ABR (profound sensoryneural hearing loss), Type III is normal OAE and absent ABR (true Auditory neuropathy). However, still complications of Al-Meqbel1 vestibular problems in ANSD are not known so far.

Background: Noise-induced hearing loss (NIHL) is one of the most common occupational illnesses. Most of the studies on NIHL were conducted at high noise levels that people are rarely exposed to but in industries. The function of the outer hair cells (OHCs) is impaired after exposure to industrial noise. Distortion product otoacoustic emissions (DPOAEs) are useful in examination of noise-induced level shifts.Objectives: To assess the function of OHCs by DPOAE temporary and permanent level shifts (TLSdp and PLSdp) in rabbits exposed to white noise at realistic levels typically found in industrial settings over a broad range of frequencies.Methods: 12 albino rabbits were divided into two groups: the experimental group rabbits which were exposed to 95 dB SPL white noise at 500-8000 Hz for 8 hrs/day for 5 consecutive days, and the control group rabbits with no exposure to noise. The function of OHCs was examined by DPOAE level (Ldp) in different occasions. The study groups were compared for DPOAE temporary and permanent level shifts (TLSdp and PLSdp) to assess the effect of noise on OHCs function.Results: Noise-induced DPOAE levels (Ldp) were decreased up to 20.65 dB (on day 8) and 18.93 dB (on day 11) at 5888.50 Hz (p=0.081). TLSdp and PLSdp were significantly decreased up to 17.99 dB and 16.27 dB, respectively in the experimental group. The most and least Ldp were significantly different (p<0.05); they occurred at 5888.50 and 588.00 Hz, respectively. There were significant differences between temporary and permanent threshold shift at various frequencies (p<0.05). These differences were mainly related to 5888.50 Hz compared to other frequencies in each ear (p<0.05).Conclusion: DPOAEs are an attractive tool for obtaining information about small temporary or permanent threshold shifts, even when the pure tone audiogram is normal.

Objectives: The aim of the present study was to assess the Auditory lateralization ability in children with (central) Auditory processing disorder.Methods: Participants were divided in two groups: 15 children with Central Auditory Processing Disorder (8-10 years) and 80 normal children (8-11 years) from both genders with pure-tone air-conduction thresholds better than 20 dB HL bilaterally and interaural pure tone threshold difference better than 5 dB.All subjects had normal IQ and normal otoscopy: In the present study 9 imaginary positions were simulated in horizontal plane by Interaural Time Difference (ITD) and Interaural Intensity Difference (IID) to evaluate the Auditory lateralization performance in normal and children with (central) Auditory Processing Disorder (C) APD. Lateralization performance were determined by ITD ranging from -880 to+880 microsecond and IID ranging from -10 to+10 dB for high pass and low pass noise (2 kHz cut off point). Boltzmann function was used to describe the Auditory lateralization performance and Independent Samples T-test was used to compare the two groups.Results: according to Boltzmann function two major types of abnormalities were revealed in the lateralization performances: 1- completely disoriented, 2- side-oriented.86.6% of (C) APD children showed significant increase in mean of test errors compared with normal ones (p<0.001).Discussion: The study supports the hypothesis that most children with (C) APD have poor Auditory lateralization and abnormal processing of binaural cues.