Materials and Methods: It is for the first time in Iran that designing and construction of phase-shifter instrument for performing Masking Level Difference have been studied. For reducing limitations of MLD test in middle ear pathologies, new methods of performing MLD has been considered.
In this method noise is conducted by bone vibrator, located on forehead. The comparison between standard method and proposed method has been obtained.Forty 20-25 year-old men referring to the Faculty of Rehabilitation Science in Iran university of Medical Sciences have been tested in the period of time between 10.30.1998 to 12.21.1998.The MLD test was performed in both method at frequencies of 250, 500, 1000, 2000 & 4000 Hz.
Results: The mean of MLD results n the standard method was 11.175 dB ranging from 10 to 13 dB that is in accordance with normative data.
- There was no significant difference between the means obtained in the methods for performing MLD.
- In both methods the MLD means decreased with frequency increments.
Conclusion: It is preferable to use proposal method in middle ear disorders due to normal cochlear sensitivity and subsequently enough noise that is conducted by bone conduction (60 dB SPL).

Objective: Survery and comparison between the physical characteristics of Distortion-Product Otoacoustic Emissions of 1-59 day-old normal-hearing newborns refered to TUMS, Rehabilitation School , Audiology department , 2002
Method & Material : This analytical-descriptive study was conducted on the ears of 102 easy method selected newborns. The tests included: otoscopy , BOA, Immittance audiometry , DPOAEs, and ABR if necessary. The amplitude and frequency of 2f1-f2 emissions of DPOAEs evoked by two pure tones (L1=65 dBSPL , L2=50 dBSPL and f2/f1=1.2) were also calculated.
Results: 1-All normal hearing newborns have normal DPOAEs. No significant difference was observed in test-retest. 2- The amplitude of the DPOAEs to the right ear is significantly greater than the amplitude of the left ear (P<00.05). 3- No significant difference was observed between newborn&aposs DPOAEs in terms of their gender.
Conclusion: DPOAEs could be measured quickly and noninvasively and are excellent tools for the screening of newborn hearing loss. The results are valid only within the Context of this research.

Background and Aim: Central auditory processing disorders (CAPD) may have a variety of etiologies therefore, performing CAPD tests seem inevitable. Behavioral tests such as synthetic sentence identification (SSI) has gained considerable popularity because of high sensitivity to brainstem and cortical lesions, high diagnostic ability,  cost-benefiting, and also limitations of electrophysiologic tests. The purpose of this study was to prepare a Farsi-language version of SSI and to perform a primary evaluation. 
Materials and Method: Farsi SSI test was made and recorded on CD. Then sixty 20-to 35- year old normal-hearing participants were evaluated in audiology clinic, Faculty of Rehabilitation Sciences Iran University of Medical Sciences in three months.
Results: There is no significant difference between scores of Farsi and original versions of SSI. Gender has no significant effect on the scores.
Conclusion: According to this results, Farsi SSI is comparable to the original one. It can, therefore, be used in CAPD test battery.

Background and Aim: There are evidences that indicate a relationship between auditory processing disorders and stuttering, and any disorder in the central auditory function can be at least one of the underlying causes of stuttering. Even though, using the most state of the art radiographic technologies, i.e. MRI, no definitive answer has been given in relative to this question. In this research, using Mask-ing Level Difference (MLD) and Synthetic Sentence Identification (SSI) tests, the central auditory function of stutters and normal group was evaluated.
Materials and Methods: In this study was analytic cross-sectional, fifteen male patients with stutter-ing and 15 male normal cases with the age range from 16 to 40 years (average age 26.78 year) were evaluated. SSI-ICM, SSI-CCM and MLD tests were performed. The results were compared in both groups.
Results: Although stutterers mean MLD was less than that of normal group, the different was not significant between stutters and normal group in SSI test in right ear at negative MCRs. There was a significant difference in ICM state, but in CCM state, there was no significant difference between the average score of two groups in various MCRs.
Conclusion: The findings of this research is compatible with those of similar researches about the SSI test and the pattern of results, probably indicates a partial dysfunction of brainstem in some of the stutters.

Background and Aim: One of the most common complaints, particularly among patients with normal or near normal low-frequency hearing, is that their voice sounds "hollow". This is associated with "Occlusion effect". The aim of this study was to comparison of occlusion effect in normal hearing subjects via Real Ear Measurement and Audiometric Bing test.
Materials and Method: Twenty volunteers with normal hearing (10 male, 10 female), with ages ranging from 18 - 24 years were enrolled in this study. First, audiometric Bing test was performed in frequencies of 250, 500, 750 and 1000 Hz. Then in real ear measurement, subjects were instructed to vocalize /â/ and /i/ for 5 seconds. Probe microphone was recorded the sound pressure in the ear canals. The degrees of occlusion effect unit were obtained for further analysis.
Results: The means of occlusion effect were present in all subjects. There was no correlation between the results of audiometric Bing test and real-ear measurement. No significant difference was obtained between genders and monaural or binaural occlusion in real-ear measurement. But in audiometric Bing test, the difference between monaural or binaural occlusion was significant(p<0.05).
Conclusion: The peak of occlusion effect varies significantly among hearing aid users, so the hearing aid must be tuned. Probe- microphone measures will assist in determination how much gain is enough, and where frequency- specific adjustments are needed.

Background and Aim: Hearing aid users complain about a phenomenon called "occlusion effect". The aim of this study was to compare the occlusion effect in normal hearing individuals and those with slight and mild sensory neural hearing loss via Real Ear Measurement.
Methods: Sixty volunteers (30 male, 30 female) aged 18-55 years were enrolled in this study. Subjects were instructed to vocalize /e/ and /i/ for 5 seconds. Sound pressure level was measured by a probe- microphone and recorded in the ear canal. Occlusion effect and the frequency in which maximum occlusion effect occurs were obtained for each individuals for further analysis.
Results: The peak of occlusion effect for /e/ was 10.25 dB and 9.77 dB respectively in 751.9 Hz and 542.98 Hz frequencies in female and male individuals. The maximum occlusion effect occurred with 19.03 dB and 19.10 dB for /i/ and in 518.88 Hz and 440.28 Hz in female and male individuals, in respect. In addition, no significant difference was seen among hearing levels and between genders.
Conclusion: The peak of occlusion effect varies significantly among hearing aid users so that the hearing aid must be tuned. Probe-microphone measures will assist in determination where frequency- specific adjustments are needed.

Background and Aim: It is well established that adult sensory systems can reorganize following environmental changes hearing aid stimulates a deprived auditory system resulting in changes in received stimuli and may be capable of inducing changes within the auditory system abilities such as difference limen for intensity. Hearing aid fitting induces perceptual and physiological modifications. The present study was conducted to evaluate the effects of hearing aid use on the intensity discrimination performance.
Methods: The study group consisted of 30 monaural users of hearing aid with symmetrical moderate or moderately severe sensorineural hearing loss in both ears (15 males, 15 females), aged 45-65 years old with the mean of 57.73 and SD of 8.12 years. difference limen for intensity was measured at two frequencies, 500 Hz, 2000 Hz, and two intensity levels (10 dB SL, 40 dB SL). The results of fitted ears were compared with not-fitted ones.
Results: The results of the study showed better difference limen for intensity scores at high frequency and high intensity levels. A significant lower difference limen for intensity in fitted ears was observed compared with not-fitted ears (p<0.05), while there was no significant difference between the difference limen for intensity in the two groups at 500 Hz with 10 dB SL intensity (p=0.132).
Conclusion: Hearing aid use affects intensity discrimination performance. Besides, perceptual modification following use of hearing aid is confirmed by our study which suggests a possible functional plasticity due to hearing aid use. However, further