The cut off points of 90th percentile of acoustic reflex thresholds were determined in the normal and sensory hearing loss.All subjects had measurable hearing(ANSI-1969≤110 dBHL) in three frequencies of 500,1000 and 2000Hz.

While hearing loss was more than 55dB, The cut off point was higher in studies that NR responses was included.

In cases that hearing loss was less than 75dB, 90th percentile can be used in diganosis of retrochochlear lesions.Since Acoustic reflexes are absent in both mentioned pathologies in greater amount of hearing loss,It would be less efficient in diffrential diganisis of cochlear and retrochochlear lesions to use acoustic reflex thresholds under the mentioned circumstances.

Auditory perceptual and visual-spatial characteristics of subjective tinnitus evoked by eye gaze were studied in two adult human subjects. This uncommon form of tinnitus occurred approximately 4-6 weeks following neurosurgery for gross total excision of space Occupying lesions of the cerebellopontine angle and hearing was lost in the operated ear. In both cases, the gaze evoked tinnitus was characterized as being tonal in nature, with pitch and loudness percepts remaining constant as long as the same horizontal or vertical eye directions were maintained. Tinnitus was absent when the eyes were in a neutral head referenced position with subjects looking straight ahead. The results and implications of ophthalmological, standard and modified visual field assessment, pure tone audio metric assessment, spontaneous otoacoustic emission testing and detailed psychophysical assessment of pitch and loudness are discussed.

Nowadays OAE have a special role in electrophysiological examinations and also remarkable application in infants&apos hearing screening test. In the current article we have focused attention on the physiological fundamentals of OAE and tried to explain the trends in physiological studies that finally led to discovering the acoustic radiations by "David Kemp". By studying this article we can conclude that inner ear cannot be pondered just as a transformer that change the movements of the inner ear&aposs fluid to the neural signal, rather it should be considered as an active organ that can produce energy and also control the other active mechanisms involved in hearing.

Recent studies have demonstrated that outer hair cells play two functional roles in the ear: one is the sensory function and the other is motor one. The function of OHCs in being trigered with very poor signals can not be overlooked. This mechanism would lead in improving the sensitivity of the ear. As stimulus intensity increases, little by little, OHC will reach its saturation level and finally the amplification effect decreases.Otoacoustic emissions could be reverberations produced by the responses of outer hair cells .Any decrease in the number of OHCs can cause a mechanical split in the fine tuning mechanism of the organ of corti and result in hearing loss.

Many of the CP angle tumors are acoustic neuroma, vestibular schowanoma or 8^th nerve tumor. This kind of tumor is benign histologically. Big size ones can cause neurological symptoms such as cerebellar imbalance, edema and cranial nerves dysfunction. Acoustic neuroma is mostly unilateral and audio logical findings manifest a unilateral hearing loss. Although big size tumors can lead to bilateral audio logical symptoms which can affect the findings of hearing assessment. Here, a 31 year-old patient suffering right ear vestibular schowanoma have been reported. changes in left ear pure tone results, acoustic reflex measurements and ABR in addition to hearing loss in the right ear have been demonstrated.

Background: hearing loss is a major health care problem that tends to retard the developmental milestones of children. It takes early detection and intervention to avoid a permanent loss in acquisition of speech and cognitive functions. Hence, the importance of hearing screening in all children especially in the developing world for accurate statistics and early intervention is clear. This work was aimed at predicting hearing in children by means of acoustic reflex measurements
Method: In this study which was performed in 1995, 146 ears(86 children aged between 5-10years old referring to audio logy clinic in Tehran university of medical sciences between august 1995 and February 1996) were evaluated (amongst 95 were normal and 51 ears with SNHL<84dB).the methods Niemeyer and Destrehan formula ,Lilly2 equation, un weighed Sensitivity prediction by acoustic reflex, weighed sensitivity prediction by acoustic reflex to establish their clinical viability.
Results: findings demonstrated that weighed sensitivity prediction by acoustic reflex(WASPAR) have a good correlation with conventional audiometric evaluation(K=.78) and also it has good sensitivity, Specificity , Negative predicted value(NPA) and positive predicted value (PPV).
Conclusion: In case that conventional audiometry is not applicable, WASPAR is a good objective choice in lieu of subjective tests.

Tinnitus from the Latin word tinnire meaning ringing is the perception of sound within the human ear in the absence of corresponding external sound. The most common cause is noise induced hearing loss. Tinnitus may be induced by an acoustic trauma or a permanent noise in the workplace. In case that Tinnitus is induced by acoustic trauma the site of lesion is commonly the base of the cochlea. Tinnitus in the senile population is mostly accompanying presbycusis. Although the incidence of permanent tinnitus following noise exposure is high, little is published about this issue. In the current article we are aimed at studying the prevalence of tinnitus in Minoo and other manufactures.

Nowadays, sound is a critical part of our daily life and its unwanted and undesirable disturbances in the environment and in the workplace has induced much psychological and physical annoyance to human being and had also lessened the efficacy of the daily activities. Since the mechanical vibrations of molecules in the air had led in producing sound and considering profound damaging vibrations produced by the harsh sounds in the objects and instruments, we have studied the noise and the vibrations caused by it, together.With this introduction and Considering the potential devastating impact of noise and the need to keep staff which are working in the control room secure from this effects the power house of "Shahjid Madhaj"  have proposed a project to control and limiting the noise in the control room by examining the diverse ways of transmitting sound into it. The project will be discussed here in details.

NIHL occurs when too much sound intensity is transmitted into and through the auditory system and can be occur following a shot gun or the exposure to a moderately intense sound for a long period of time. NIHL caused by acoustic trauma refers to permanent cochlear damage from a one-time exposure to excessive sound pressure. This form of NIHL commonly results from exposure to high-intensity sounds such as explosions, gunfire, a large drum hit loudly and firecrackers.Meanwhile the sound intensity, duration of exposure and personal hearing thresholds as the effective factors in the amount of noise induced hearing loss should not be overlooked.  Since numerous investigations have been performed about intense sudden sound we will discuss it in detail in the current article.

Many researchers have reported that after the sound trauma, RNA and DNA in the outer hair cells and ganglion cells will decrease. Some scientists have also mentioned the mitochondrial enzyme deficits in cochlear cells. Sound stimulation will induce the decrease of enzyme activities which are effective in the process of energy production. This process happens because of the reduced ATP synthesis and in turn the damage to receptors due to energy disruption.  The moderate oxygen deficiency can also be considered as a potential factor in the amplitude changes of the potential of cochlear microphonic due to irrita6ing sounds. On the other hand, since the organ of corti is far from blood tissue, logically, Anaerobic Glycogen should be considered as the main factor in the metabolism of the organ of corti.In addition to that, there are evidences which demonstrate intense acoustical stimulation can increase Na+ and decrease K+ in endolymphatic fluid and a contrary effect in perylimphatic fluid in scala vestibule.

Method and Materials :this cross sectional descriptive and analytic survey was done at Golestan navy hospital in Tehran, between June 1998 and March 1999 on total of 69 male subject (104 ears, ) 50 acoustic trauma & 54 noise induced H.L) between 20 to 40 ears old.
Results:1- The mean acoustic reflex threshold at 1 kHz showed there is no significant difference between two groups.
2- The intensity elicited maximum reflex amplitude at 1 kHz didn&apost produce at a significant linear correlation with subject&aposs age and ear canal volume in both groups.
3- The intensity elicited maximum reflex amplitude in NIHL group wasn&apost shown a significant correlation with ear compliance and gradient.
4- The mean Intensity (SPL) elicited maximum reflex amplitude in NIHL group was more than mean intensity (SPL) in acoustic trauma group.
5- The mean intensity (SL) elicited maximum reflex amplitude in NIHL group was More than mean intensity (SL) in acoustic trauma group.
Conclusion: Acoustic reflex amplitude is reduced for subjects with NIHL compared with acoustic trauma subjects.

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.

In addition to Stimulus frequuncy and level, emitting Inner ear structurs status, OAEs parameters depend on conductive sound pathways charactristics, so abnormal OAEs donot always represent cochlear abnormality. Middle ear transmites Vibrations in two directions: forward and backward. Middle ear pathologies affect both forward and backward transmission.In this paper, The purpose is investigation of immediate effects of tympanic over - and under - pressure on click evoked Otoacoustic Emissions (CEOAEs) in healthy individuals. Healthy subjects with normal hearing and middle ear were exposed to ambient pressure changes in a pressure champer. The pressure was progressively changed in 100 dapa steps to accomplish on increase and decrease  in tympanic pressure. Pressure equilibration of the middle ear was avoided. The relative tympanic over-and under - pressure (+/-320 dapa) was monitored by tympanometry and CEOAEs recorded at every step of tympanic pressure change. The CEOAEs recorded during progressive tympanic over-and under- pressure had reduced amplitude and shorter latencies that were most pronounced in the 750 to 3000 Hz frequency bands.

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.

Objective: This study was aimed to survey the hearing status of the patients with definite MS. The results of this study may help to confirm the diagnosis and to improve our knowledge of different aspects of this disease and to optimize the treatment and rehabilitative techniques.
Material & Methods: This study is performed in audiology clinic of rehabilitation science faculty of Iran medical science university as an assesive-analytic procedure in winter of 2000 in 40 MS patients (Referred from the MS clinic of Shohada Hospital) of 20 to 45 years old. All the patients have no history of otologic problems. The results of conventional audiologist tests (PTA, SRT, SDS, imittance audiometry) and ABR findings of MS patients were compared to the results of control group.
Results: The differences between the means of low, high and mid frequency PTAve in MS patients and control group were statistically significant (P<0.05). There was no significant difference between two groups in the speech test&aposs results, statistically. The results of ART test show statistically significant differences between experimental and control groups. The only differences in ABR results were seen for the absolute latency of the wave V and IPLs (I-V, III-V) between two groups. The amplitude ratio of V/I in MS patients 1.5 was within the normal range (0.5 to 2). There was a statistically significant relationship between mean of mid frequency PTAve and prolongation of absolute latency of the wave V. The relationship between ABR and SDS and also between ART and ABR were not statistically significant. Finally, the results of this study suggested that low, high and mid frequency PTAve, ART, absolute latency of the wave V, and IPLs III-V, I-V can be used ascomplementory method to confirm the diagnosis of MS with other conventional methods such as: MRI, CSF analysis, SEP and VEP.

Objective: OAE an audiologic study for diagnosis of exteracochlear auditory neuropathy.
Method & Material: Immitance audiometry, OAE and ABR and rehabilitation Intervention was performed for 3 children suffered from kernictrus.
Conclusion: 1) OAE in the from of screening, distorted product and transient evoked-otoacoustic emission has to be added to our audiology test battery. 2) OAE studies have their own merit when we are clinically involved with the diagnosis of especial clinical entities like neonatal hypoxia, kernicterus, multiple sclerosis, meningitides and meningoencephalitis. 3) Case selection for cochlear implantation needs a knowledge of patients' OAE results. 4) In the case of intracerebral auditory neuropathy the need for other rehabilitative measures will be better understood.

Objective : To assess neonates and children suffering from meningitis , during the critical and recovery periods , using ABR , EOAE and Behavioral Audiometry.
Method and Material: 40 neonates to 12-year-old children were assessed. Using ABR test, the hearing of these cases was evaluated during the critical period-that is , 24-72 hours following the diagnosis. This test was repeated when patients recovered from meningitis-that is 24 hours before discharge (recovery period) Hearing function , again , was assessed 7-14 days following discharge through Immittance Audiometry, Behavioral Audiometry (PTA , SF and BOA). And EOAE (TEOAE and DPOAE) tests procedures.Findings: During the critical period , ABR test revealed normal hearing in 35 patients (87.5%) and severe to profound sensorineural hearing loss (unilateral and bilateral) in 5 patients (12.5%-girl=4, boy=1). The same result were obtained in re-evaluation in the recovery period. On the other hand , 7-14 days after of discharge , Immittance Audiometry and Behavioral Audiometry (including PTA , S.F and BOA tests), confirmed the mentioned results (cross - gcheck). EOAE test (DPOAE and TEOAE) in 35 normal hearing patients (according to ABR test) , showed normal cochlear function. 2 out of 5 cases suffering from severe to profound sensorineural hearing loss revealed normal cochlear function. According to EOAE results , abnormal cochlear function was evident in 3 patients.
Conclusion: ABR , EOAE tests , and Behavioral Audiometry in children meningitis during the critical period and recovery period can be used to diagnose any degree of hearing loss with a high level accuracy. The results of persent study is confirmed by previous investigations.

Background and Aim: Hearing sensitivity is so vital for musicians as loud music can cause hearing loss. The aim of this study was to assess hearing sensitivity of musicians in order to determine the effects of music exposure on hearing organ.
Materials and Methods: This case-control study  was conducted on 15 string musicians with musicianship history of more than 10 years and 15 normal hearing subjects. They all were male and 20-30 years old. TEOAEs and DPOAEs performed after otoscopy , immittance and pure tone audiometry in octave frequencies between 250 to 16000 Hz.
Results: There is not significant difference between pure tone thresholds of two groups for all frequencies.A significant difference of TEOAE is found between two groups for total response and amplituds of TEOAEs . DPOAEs amplituds are not significantly different between two groups .
Conclusion: Musicianship may  affect TEOAEs amplitudes , but cannot affect results of PTA and DPOAEs. Therefore this can be useful to detect cochlear lesions secondary to music exposure and also as a tool in hearing protection program.

Background and Aim: Hyperbilirubinemia is one of the most common abnormalities during the neonatal period. Approximately 60% full-term and 80% preterm neonates suffer from hyperbilirubinemia. Hearing loss is one of the most prevalent side-effects of hyperbilirubinemia. This happens when the serum concentration of indirect bilirubin increases dramatically. The main purpose of this study is to evaluate the hearing status and to diagnose the probable site of lesion in affected children.
Materiads and Methods: In this cross-sectional study, 33 newborn to two year old subjects uffering from hyperbilirubinemia were evaluated using auditory brainstem response (ABR) and transient evoked otoacoustic emissions (TEOAE) tests In the Audiology department of the Faculty of Rehabilitation Sciences Iran University of Medical Sciences sampling method was accessible.
Results: 21% of the subjects had severe to profound hearing loss and 9% of subjects had mild to moderate hearing loss. In 51% of the subjects there was no response to ABR and TEOAE tests indicating cochlear and/or retrocochlear lesion. The other 15% manifest only abnormal ABR test indicating the presence of the auditory neuropathy.
Conclusion: TEOAEs test has its own limitations in these subjects, that is the hearing status of such patients can not be completely evaluated by using just TEOAE test. Therefore, to detect hearing loss both ABR and TEOAE tests must be performed in these subjects.