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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).

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Background: In recent years there has been increased interest in the use of Al for assessing hearing handicap and for measuring the potential effectiveness of amplification system.AI is an expression of proportion of average speech signal that is audible to a given patient, and it can vary between 0.0 to 1.0.
Method and Materials: This cross-sectional analytical study was carried out in department of audiology, rehabilitation, faculty, IUMS form 31 Oct 98 to 7 March 1999, on 40 normal hearing persons (80 ears 19 males and 21 females) and 40 hearing impaired persons (61 ears 36 males and 25 females, 25-65 years old) with moderate to moderately severe SNI-IL The pavlovic procedure (1988) for calculating Al, open set taped standard mono syllabic word lists, and the real -ear probe- tube microphone system to measure insertion gain were used, through test-retest.
Results: 1/A significant correlation was shown between the Al scores and the speech recognition scores of normal hearing and hearing-impaired group with and without the hearing aid (P<0.05) 2/ There was no significant differences in age group & sex: also 3 In test-retest measures of the insertion gain in each test and 4/No significant in test-retest of speech recognition test score.
Conclusion: According to these results the Al can predict the unaided and aided monosyllabic recognition test scores very well, and age and sex variables have no effect on its ability. Therefore with respect to high reliability of the Al results and its simplicity, easy -to- use, cost effective, and little time consuming for calculation, it&aposs recommended the wide use of the Al, especially in clinical situation.

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Objective: As the cerebrovascular diseases (CVD) are among the most common anomalies that are directly or indirectly affecting the auditory cortex, studying in this area is important. We tried to evaluate the function of CANS in a group of 50-70 years old cerebrovascular accident (CVA) patients with no hearing complaint by competing sentences test (CST) as a dichotic speech test.
Method and Material: This cross-sectional analytical study was conducted at Loghman-e-Hakim hospital between 22, august 1999 and 20, July 2000 in a group of 30 normal 50-70 years old persons and a group of 40 patients with CVA including 30 patients with abnormal CT scan and 10 patients with normal CT scan.
Results: The results point out the mean scores of CST in the normal group were at normal range (80-100%) in both ears. And mean scores of CST decreased in the patients groups. There were significant difference between mean scores of CST in the patients with CVA and control groups. Conclusion: CST seems to be a valuable test in the CANS test batteries for the cerebrovascular diseases.

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Background and Aim: Mismatch negativity (MMN) is one of auditory evoked potentials that occurs about 100-250 ms after stimulus onset. The MMN waveform is elicited by a discriminateable change in a sequence of repetitive homogenous stimuli. This change can be in intensity level, frequency, or duration of auditory stimuli. The purpose of this study was to obtain MMN waveform using tonal stimuli and to investigate its changes during changes in age.
Materials and Methods: The study was prescriptive-analytic cross-sectional. The participants were sixty children aged 4 to 9 year.The Stimuli were at 80 dB pe SPL. A 1000Hz tone and a 1500 Hz tone were used as standard and deviant stimuli, respectively. Probability of deviant stimuli was 20%. Trials were recorded using surface electrode placed at four locations on the head.
Results: The MMN waveform does not exist in 22.5% of the children. Also, determining of MMN peak in 22.5% was not exactly possible. In other subjects, a significant negative correlation was observed between latency of MMN and age, but not for age and amplitude for this negativity.
Conclusion: This study confirms that the MMN may not be seen in normal people. Also there are maturational changes in MMN waveform.

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Background and Aim: Contralateral stimulation with noise can improve auditory intensity discrimination. This may be related to function of the efferent system. The purpose of this study was to determine the relationship between the auditory intensity discrimination and the efferent system function.
Methods: Twenty students with normal hearing were included in this descriptive-analytic study. We examined Difference Limen for Intensity (DLI), Otoacoustic Emissions suppression and Speech In Noise. DLI was evaluated with and without contralateral noise stimulation at two different stimulus levels (20, 70 dB SL).
Results: There was significant difference between mean DLI scores of with contralateral masking comparing to without it, which was more prominent as frequency increased. Mean DLI score while masking with white noise was more than mean scores when masking with narrow band noise (p<0.05). Transient evoked otoacoustic emissions responses decreased significantly in amplitude with contralateral masking. (p<0.05)
Conclusion: These results suggest that medial olivocochlear bundle functions as a key role in auditory intensity discrimination.

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Background and Aim: Learning disability is a term referes to a group of disorders manifesting listening, reading, writing, or mathematical problems. These children mostly have attention difficulties in classroom that leads to many learning problems. In this study we aimed to compare the auditory attention of 7 to 9 year old children with learning disability to non- learning disability age matched normal group.
Methods: Twenty seven male 7 to 9 year old students with learning disability and 27 age and sex matched normal conrols were selected with unprobable simple sampling. 27 In order to evaluate auditory selective and divided attention, Farsi versions of speech in noise and dichotic digit test were used respectively.
Results: Comparison of mean scores of Farsi versions of speech in noise in both ears of 7 and 8 year-old students in two groups indicated no significant difference (p>0.05) Mean scores of 9 year old controls was significant more than those of the cases only in the right ear (p=0.033). However, no significant difference was observed between mean scores of dichotic digit test assessing the right ear of 9 year-old learning disability and non learning disability students (p>0.05). Moreover, mean scores of 7 and 8 year- old students with learning disability was less than those of their normal peers in the left ear (p>0.05).
Conclusion: Selective auditory attention is not affected in the optimal signal to noise ratio, while divided attention seems to be affected by maturity delay of auditory system or central auditory system disorders.

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Background and Aim: The dichotic auditory-verbal memory test (DAVMT) is useful in detecting auditory-verbal memory deficits and differences in memory function between the brain hemispheres. The purpose of this study was to prepare the Persian version of dichotic auditory-verbal memory test and to obtain its results in 18- to 25-year old normal individuals of both genders in Iran.
Methods: The Persian version of dichotic auditory-verbal memory test like the original one consisted of 18 lists of ten words. The lists were arranged such that 10 words were presented to one ear, with the reverse words simultaneously were presented to the other ear, constituting a dichotic test situation. After preparing the 18 lists, content validity was assessed by a panel of eight experts and then, the words of each list were recorded on CD in a dichotic mode. Thereafter, it was performed on one hundred and ten normal individuals with ages ranging from 18 to 25 years (mean age: 21.3 SD 1.9 years) and the scores were recorded on a specially designed scoring sheet.
Results: There was no significant difference between mean scores of 18 lists of the dichotic auditory-verbal memory test. The overall mean of CVI was 96% for the 18 lists and the mean score of dichotic auditory-verbal memory test was 6.5 SD 1.0 in the normal group.
Conclusion: Based on the obtained results, the Persian version of dichotic auditory-verbal memory test has a good content validity and can be used in detecting the auditory-verbal memory deficits.

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Background and Aim: Temporal resolution refers to the ability of perceiving changes over time. This study was conducted to prepare Persian version of the temporal resolution test, which was first introduced by Phillips (1994) and Stuart (1996), and to obtain its results in 18 to 25 year old normal individuals of both genders.
Methods: To construct the Persian version of the temporal resolution test, like the original version, speech stimuli, continuous and interrupted noises were used. Speech stimuli comprised four lists of fifty words-monosyllabic lists, which were presented to the right ears first in quietness and then with continuous and interrupted noises on S/Ns of -20, -10, 0, +10 dB. The test was performed on thirty three right handed healthy individuals (14 male and 19 female with the mean age 21.02, SD=1.7 year old) in written response mode.
Results: Significant difference was shown between test scores in quiet with each of the continuous (p<0.0001) and interrupted (p≤0.0001) noises in four signal to noise ratios, and also between test scores of continuous and interrupted noise presentations (p<0.0001). No significant correlation was revealed between gender and test scores and age and test score and age in +10 dB S/N ratio.
Conclusion: Conducting this test on a group of healthy individuals showed its application for measuring temporal resolution with speech stimuli.

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Background and Aim: Bilingualism, as one of the discussing issues of psychology and linguistics, can influence the speech processing. Of several tests for assessing auditory processing, dichotic digit test has been designed to study divided auditory attention. Our study was performed to compare the auditory attention between Iranian bilingual and monolingual young adults.

Methods: This cross-sectional study was conducted on 60 students including 30 Turkish-Persian bilinguals and 30 Persian monolinguals aged between 18 to 30 years in both genders. Dichotic digit test was performed on young individuals with normal peripheral hearing and right hand preference.

Results: No significant correlation was found between the results of dichotic digit test of monolinguals and bilinguals (p=0.195), and also between the results of right and left ears in monolingual (p=0.460) and bilingual (p=0.054) groups. The mean score of women was significantly more than men (p=0.031).

Conclusion: There was no significant difference between bilinguals and monolinguals in divided auditory attention and it seems that acquisition of second language in lower ages has no noticeable effect on this type of auditory attention.

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Background and Aim: Staggered spondaic words (SSW) test examines central auditory nervous system . Some researches show stuttering causes hyperactivity in motor system of the right hemisphere and cerebellum and decreases activity in the left hemisphere. During stuttering also, central auditory processing is decreased . The aim of this study was to compare the Persian staggered spondaic word test results between persistent developmental stutterers and normal subjects.

Methods: Thirty people with persistent developmental stuttering were participants of this cross-sectional descriptive-analytic study, which were aged 11 to 40 years. The control group matched for gender and number with stutters. They were 8 females and 22 males, with the age of 11 to 40 years, without any stuttering history, neurological diseases and auditory disorders.

Results: Stutterers were in normal category in corrected staggered spondaic words test. The mean scores of errors of right compete, right ear, left compete, left ear and total in corrected s taggered spondaic words between control and stuttering group showed significant differences. There was a significant relationship between stuttering and effect, too (p<0.05).

Conclusion: Based on the obtained results of this study, stutterers may have different cortical and sub - cortical brain activity than people who have not stutter . Central auditory processing abilities of stutterers are weaker than normal people.

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Background and Aim: Cerebrovascular accident is a neurological disorder involves central nervous system. Studies have shown that it affects the outputs of behavioral auditory tests such as dichotic auditory verbal memory test. The purpose of this study was to compare this memory test results between patients with cerebrovascular accident and normal subjects.

Methods: This cross-sectional study was conducted on 20 patients with cerebrovascular accident aged 50-70 years and 20 controls matched for age and gender in Emam Khomeini Hospital, Tehran, Iran. Dichotic auditory verbal memory test was performed on each subject.

Results: The mean score in the two groups was significantly different (p<0.0001). The results indicated that the right-ear score was significantly greater than the left-ear score in normal subjects (p<0.0001) and in patients with right hemisphere lesion (p<0.0001). The right-ear and left-ear scores were not significantly different in patients with left hemisphere lesion (p=0.0860).

Conclusion: Among other methods, Dichotic auditory verbal memory test is a beneficial test in assessing the central auditory nervous system of patients with cerebrovascular accident. It seems that it is sensitive to the damages occur following temporal lobe strokes.

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Background and Aims: The dichotic listening subtest is considered as an important component of the test battery for auditory processing assessment in both children and adults. A randomized dichotic digits test (RDDT) was created to compensate for sensitivity weakness of double digits when detecting abnormal ear asymmetry during dichotic listening. The aim of this study was the development and initial evaluation of the Persian randomized dichotic digits test.

Method: Persian digits 1-10 (except for the bisyllabic digit, 4) uttered by a native Persian language speaker were recorded in a studio. After alignment of intensity and temporal characteristics of digit waveforms, lists 1 and 2 of the RDDT were reproduced. List 1 of the test was administered at 55 dBHL on 50 right-handed normal hearing individuals (with an equal sex ratio) in the age group of 18-25 years and hearing thresholds of 15 dBHL or better in audiometric frequencies.

Results: Mean (standard deviation) percent-correct score for right and left ears and right ear advantage of the subjects was 94.3 (5.3), 84.8 (7.7), and 9.5 (7.0) percent, respectively. Sixty percent of the subjects showed normal results and unilateral and bilateral deficits were seen in 24 percent and 16 percent, respectively.

Conclusion: It seems the Persian version of RDDT is the same as the original test as it is able to test ear asymmetry , unilateral and bilateral deficits in dichotic listening.