OAEs are sound founds in the external aditory meatus that originate in the cochlea. OAEs are generated only when the organ of corti is in near normal condition and They can be detected only when the middle ear system is operating normally. The sound generated by the cochlea are small but  potentially audible, sometimes as much as 30 dBSPL. They can emerge spontaneously in the cochlea, but more commonly OAEs follow acoustic stimulation. No electrod are needed to  observe OAEs. In fact, microphone are used to detect them.

Method & Material: This study was performed on 36 normal-hearing subjects aged 18-25 years for survey of temporary threshold shift (TTS) by transient evoked otoacoustic emissions. Finding: Noise can affect the pure-tone thresholds and (TEOAEs) amplitudes. When cochlea affected by noise, evaluating TEOAE is more suitable than pure-tone audiometry. Because of this test, is objective an unaffected by attention and alertness and can be evaluated in difficult to test subject and also have high carefulness and can be performed in a quiet, but not sound-proof room.

Background and Aim: One of the most significant complaints of children with learning disability (LD) is difficulty in understanding speech in the presence of background noise. Different studies have shown that the medial olivocochlear bundle(MOCB) may play a role in hearing in noise. The MOCB function can be evaluated by the contralateral suppression of tone burst evoked otoacoustic emissions (TBEOAEs).The aim of the present study was to evaluate frequency specifications of MOCB by the contralateral suppression of TBEOAEs at 1,2,3 and 4 KHz in response to contralateral white noise in LD students.
Materials and Methods: This case-control study was conducted on 34 LD students aged 7-11 years and 31 normal students matched for age.The contralateral suppression of TBEOAEs was evaluated by comparing TBEOAEs amplitudes with and without contralateral white noise.
Results: In the absence of noise there was no significant difference between TBEOAEs amplitudes of two groups. In the presence of noise significant decrease was seen in TBEOAEs amplitudes at 1,2,3 and 4 KHz in both groups. In LD students the amount of this decrement at 1,2 and 4 KHz was lower than in the normal students.
Conclusion: A significant diminished suppression effect at 1,2 and 4 KHz in LD students indicates that at these frequency regions MOCB function was reduced. Therefore its suggested that the assessment of MOCB by evaluating the suppression effect of TBEOAEs included in the test battery approach used in the diagnostic of LD students.

Background and Aim: A common complaint of children with learning disability (LD) is difficulty in understanding speech in the presence of background noise. Evidence from animal and human studies has indicated that the medial olivocochlear bundle (MOCB) play a role in hearing in the presence of noise. The MOCB function can be evaluated by the suppression effect of the click evoked otoacoustic emission (CEOAEs) in response to contralateral white noise. The present study was conducted to compare the suppression effect of CEOAEs between LD and normal students.

Materials and Method: This research is an analytic-interventional study. The study group consisted of 20 learning disabled and 20 normal male students. The suppression effect of CEOAEs was evaluated by a comparison between CEOAEs levels in two conditions- with and without presentation of contralateral white noise.

Results: In the absence of noise there was no significant difference between CEOAEs amplitudes of two groups while there was significant difference between CEOAEs of two groups in the presence of noise. The suppression effect of CEOAEs in normal students had significant difference with LD students.

Conclusion: The reduced suppression effect in LD students indicates the reduced activity of the MOCB function and efferent pathway in LD students which affect their ability to hear in the presence of background noise. Consequently, the suppression effect of CEOAEs can be used in the test battery approach of LD children.

Background and Aim: Matching a mother wavelet to class of signals can be of interest in signal analysis and denoising based on wavelet multiresolution analysis and decomposition. As transient evoked otoacoustic emissions (TEOAES) are contaminated with noise, the aim of this work was to provide a quantitative approach to the problem of matching a mother wavelet to TEOAE signals by using tuning curves and to use it for analysis and denoising TEOAE signals. Approximated mother wavelet for TEOAE signals was calculated using an algorithm for designing wavelet to match a specified signal.
Materials and Methods: In this paper a tuning curve has used as a template for designing a mother wavelet that has maximum matching to the tuning curve. The mother wavelet matching was performed on tuning curves spectrum magnitude and phase independent of one another. The scaling function was calculated from the matched mother wavelet and by using these functions, lowpass and highpass filters were designed for a filter bank and otoacoustic emissions signal analysis and synthesis. After signal analyzing, denoising was performed by time windowing the signal time-frequency component.
Results: Aanalysis indicated more signal reconstruction improvement in comparison with coiflets mother wavelet and by using the purposed denoising algorithm it is possible to enhance signal to noise ratio up to dB.
Conclusion: The wavelet generated from this algorithm was remarkably similar to the biorthogonal wavelets. Therefore, by matching a biorthogonal wavelet to the tuning curve and using wavelet packet analysis, a high resolution time-frequency analysis for the otoacoustic emission signals is possible.

Background and Aim: Hyperbilirubinemia during the neonatal period is known to be an important risk factor for neonatal auditory impairment, and may reveal as a permanent brain damage, if no proper therapeutic intervention is considered. In the present study some electroacoustic and electrophysiologic tests were used to evaluate function of auditory system in a group of children with severe neonatal Jaundice.
Materials and Methods: Forty five children with mean age of 16.1 14.81 months and 17 mg/dl and higher bilirubin level were studied, and the transient evoked otoacoustic emission, acoustic reflex, auditory brainstem response and auditory steady-state response tests were performed for them.
Results: The mean score of bilirubin was 29.37± 8.95 mg/dl. It was lower than 20 mg/dl in 22.2%, between 20-30 mg/dl in 24.4% and more than 30 mg/dl in 48.0% of children. No therapeutic intervention in 26.7%, phototherapy in 44.4%, and blood exchange in 28.9% of children were reported. 48.9% hypoxia and 26.6% preterm birth history was shown too. TEOAEs was recordable in 71.1% of cases. The normal result in acoustic reflex, ABR and ASSR tests was shown just in 11.1% of cases. The clinical symptoms of auditory neuropathy were revealed in 57.7% of children.
Conclusion: Conducting auditory tests sensitive to hyperbilirubinemia place of injury is necessary to inform from functional effect and severity of disorder. Because the auditory neuropathy/ dys-synchrony is common in neonates with hyperbilirubinemic, the OAEs and ABR are the minimum essential tests to identify this disorder.

Background and Aim: Contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) test evaluates the efferent auditory system. In this test, acoustic reflex is an important confounding variable. In recent years, application of this test is growing especially in children suspect to central auditory processing disorder. Therefore, the magnitude of influence of this confounding variable on the suppression of TEOAEs should be made clear. The aim of this study was to investigate the impact of acoustic reflex on contralateral suppression of TEOAEs.
Methods: This research was performed on 39 normal-hearing adults of both sexes and of 18-26 years of age. Tests were used for the determination of interaural attenuation (IA), acoustic reflex, TEOAEs and contralateral suppression of TEOAEs.
Results: TEOAEs amplitudes and their contralateral suppression were significantly higher in females and males respectively (p=0.01). The amount of TEOAEs suppression before reflex activity ranged between 2000 to 3000 Hz. Activation of acoustic reflex significantly increased the magnitude of suppression in all frequency bands (p≤0.01) and maximum suppression occurred in 500 to 1000 Hz.
Conclusion: For achieving accuracy of clinical findings, clinicians should always use suppressant levels lower than the acoustic reflex threshold. It is recommended that different norms for males and females be used in contralateral suppression of TEOAEs.