Background and Aim: Concerning the prevalence of autism spectrum disorder, many studies have examined the various aspects of this disorder. One of the major problems in autism is the sensory processing deficit, and in particular the abnormalities of auditory processing. In this review article, we have tried to explain the neurological features of auditory processing and abnormalities in auditory evoked responses in autism, finally recount some of the main methods of auditory rehabilitation.
Recent Findings: We searched for articles in databases with keywords of “autism,” “auditory processing” and “auditory rehabilitation.” A total of 102 articles were initially found in this field. Some articles were not about our study topic, thus in the end, only 79 articles were entered the study published from 1989 to 2018. Based on these studies, autism associates with a weakness in sensory integration due to abnormal interactions between different neural networks. This condition of auditory modality are being manifested as different abnormalities in evoked responses, especially for complex stimuli at the level of the brainstem and cortex. Language and speech problems are prevalent in many patients with autism, which has already been mentioned in numerous studies. To treat these deficits, appropriate auditory rehabilitation techniques (often using music to improve the symptoms) have been developed.
Conclusion: In order to know more about autism and adopt appropriate interventions, doing audiometric, behavioral and electrophysiological evaluations are recommended on a regular basis. Rehabilitation in this disorder generally include music therapy, signal-to-noise enhancement strategies, and cognitive behavioral therapies.

Background and Aim: Acceptable noise level (ANL) test is a reliable measure of people’s ability to tolerate background noise. Central nervous system is one of the determinant factors in subject’s tolerance of noise. Bilinguals’ different central activity pattern may yield different ANL test results from monolinguals. This study aims to compare noise tolerance function in Arabic-Persian bilinguals with Persian monolinguals via Persian version of ANL.
Methods: In the present study, the Persian version of ANL was administered on 115 cases with normal hearing (56 male, 59 female) aged 18–37 years in three groups of the Persian monolingual, sequential Arabic-Persian bilinguals, and simultaneous Arabic-Persian bilinguals.
Results: The statistical analysis revealed significant difference in most comfortable level (p = 0.002) and background noise level (p = 0.011) among three groups, i.e. between Persian monolinguals and sequential Arabic-Persian bilinguals and between Persian monolinguals and simultaneous Arabic-Persian bilinguals. In other words, mean scores of bilingual were higher than monolingual scores. There was no significant difference among three groups with regard to ANL scores (p = 0.114).
Conclusion: Despite the difference between Persian monolinguals and Arabic-Persian bilinguals in most comfortable level and background noise level, there is no significance difference in ANL results. Therefore, auditory central processing acts similarly in normal hearing monolingual and bilingual subjects. As a result, Persian version of ANL can be used for Arabic-Persian bilinguals, too.

Background and Aim: The auditory brainstem response (ABR) is one of the most common objective hearing tests conducting in animal and human. The purpose of this study was evaluating the morphology variations of ABR waveforms in rats with low and high rate click stimuli.
Methods: First, rats with ABR thresholds higher than 55 dB SPL were excluded and total 81 ears remained in study. Absolute and interpeak latencies of wave I, II, IV were evaluated at low (17.7 Hz) and high rate (88.7 Hz) for click stimuli at 120 dB SPL.
Results: At low rate stimuli, ABR waveforms showed different morphologies. The most common complex for waves II to IV was wave III placed on downward slope of wave II (71% of cases). Almost the same morphologies were seen at higher rate; but in some waves, it rounded and decreased amplitude. For waves IV-V, the most common morphology was equal amplitude of wave IV and V in low and high rates (35% vs 56%, respectively). Generally, the high rate stimuli didn’t severely change morphology patterns except for later waves.
Conclusion: Normal click-evoked ABR could result in different waveforms. Using click stimuli at low and high rate result in different morphology patterns. Recognizing morphology variations of ABR waveforms are essential for detecting any pathological conditions. The high rate stimuli increased latencies, especially for later waves.

Background and Aim: Children have more difficulty in understanding speech in noisy environment than adults. Different tests are available for evaluation of speech perception ability in noise in children, each examines different levels of auditory system. The present study aimed to obtain normative data for consonant-vowel in noise test for 8–12 years old Persian-speaking children.
Methods: A hundred and sixty children were selected in five age range groups of 8 to 12 years old (32 children in each age range) with normal hearing from school students in Tehran. The audiometry test was performed in octave interval between 500–4000 Hz. Then the consonant-vowel test was first performed in silence and then in signal-to-noise ratios (SNRs) of +12, +6, 0, −6, −12, at the listening comfort level and randomly in children ears.
Results: There were significant differences between age range of 8 and 9 years with other age groups in the SNR of −12. There was a significant difference in all children between the scores of left and right ears in −12, −6, 0 SNRs (p < 0.05). However, there was no specific pattern in each age group. The results showed that with increasing SNR, the scores of recognition of the syllables increased. Sex had no effect on consonant-vowel recognition in the presence of noise.
Conclusion: Recognition of the consonant-vowel in high SNR in both ears is stable before age 8, and this stability in the low signal-to-noise ratio is higher at around the age of 10.

Background and Aim: In most everyday settings, speech is heard in the presence of competing sounds and speech perception in noise is affected by various factors, including cognitive factors. In this regard, bilingualism is a phenomenon that changes cognitive and behavioral processes as well as the nervous system. This study aimed to evaluate speech perception in noise and compare differences in Kurd-Persian bilinguals versus Persian monolinguals.
Methods: This descriptive-analytic study was performed on 92 students with normal hearing, 46 of whom were bilingual Kurd-Persian with a mean (SD) age of 22.73 (1.92) years, and 46 other Persian monolinguals with a mean (SD) age of 22.71 (2.28) years. They were examined by consonant-vowel in noise (CV in noise) test and quick speech in noise (Q-SIN) test. The obtained data were analyzed by SPSS 21.
Results: The comparison of the results showed differences in both tests between bilingual and monolingual subjects. In both groups, the reduction of signal-to-noise ratio led to lower scores, but decrease in CV in noise test in bilinguals was less than monolinguals (p < 0.001) and in the Q-SIN test, the drop in bilinguals’ score was more than monolinguals (p = 0.002).
Conclusion: Kurd-Persian bilinguals had a better performance in CV in noise test but had a worse performance in Q-SIN test than Persian monolinguals.

Background and Aim: One of the tools for assessing the vestibulo-ocular reflex (VOR) is using video head impulse test (vHIT). In this test by placing the head at different angles and shaking the head, three semicircular canals of the vestibular system in each ear can be examined separately. The purpose of this study was to investigate the relationship between the low and high velocities of the vHIT test with VOR and its compensatory saccades.
Methods: The vHIT test was performed by an examiner in 49 normal individuals aged 23–39 at low and high velocities. All participants had normal hearing, visual, and vestibular systems.
Results: Mean gains in the horizontal, anterior and posterior semicircular canals in the right ear respectively were 0.92, 1 and 0.90 and in the left ear 0.93, 0.99 and 0.95 for low velocity and 0.78, 0.92 and 0.79 in the right ear and 0.80, 0.85 and 0.86 in the left ear for high velocity. Also, the number of compensatory saccade at high velocity was higher than those at the low velocity and the latency of compensatory saccade was lower at the higher velocity.
Conclusion: In the vHIT test, VOR gain decreases at high velocity that is statistically significant. Also, compensatory saccades are more likely to occur at high velocity with smaller delay. Therefore, high-velocity vHIT test is not recommended for the purpose of examining the VOR gain and compensatory saccade.

Background and Aim: Aging affects the auditory lateralization function that is achieved thr­ough processing binaural cues. One of the most important benefits of this process, along with getting informed of sound location, is increasing signal to noise ratio and improvement of speech comprehension in crowded environments, which is one of the most common hearing complaints in the elderly. This study aimed to compare the performance of the lateralization function under the headphone conditions between the elderly and the youth, with a filtered noise stimulus.
Methods: This study was performed between 22 elderly aged 60−80 and 22 young people aged 20−30. The auditory threshold was less than 25 dB HL in 250 to 4000 Hz frequencies in both groups. By applying a time delay of −880 to +880 microsecond and the intensity difference of −10 to +10 dB between the two ears, and with high-pass and low-pass noise stimulus, the lateralization function was examined. For description of the lateralization function, scatter diag­ram and in order to compare the results, paired t-test and independent t-test were used.
Results: Findings showed that the elderly's errors were increased in all tests compared to those of the youth group. There was a significant difference (p < 0.05) between the two groups in lateralization by time clues with low-pass and high-pass noise.
Conclusion: Results confirm the impairment of the lateralization and processing of binaural cues in the elderly differently.

Background: Subjects with (central) auditory processing disorder (C)APD may manifest a range of complaints including difficulty in speech perception in noise, following directions, and discrimination of similar speech sounds. Other disorders may also have the same behavioral manifestations.
The Case: Here we present an 8-year-old boy who was misdiagnosed and mismanaged as a child with learning disability. His speech, language and cognition problems at initial evaluation included semantic problem, a short length of speech, phonological sound disorder, and attention disorder. He showed abnormality in the dichotic digits test with free recall approach and monaural selective auditory attention test. Based on his performance and test results, he was suffering from (C)APD especially in dichotic listening and speech perception in competition. It was suggested that binaural hearing training with differential interaural intensity, informal localization training including localization clock, and auditory training in noise be added to his classic auditory training program.
Conclusion: Studying this subject was important because (C)APD diagnosis needs a team approach. Evidently, the parents, teacher and speech-language pathologist (SLP) did not seek a central auditory processing evaluations early enough but some of his behaviors could potentially be a red flag for (C)APD and could guide SLPs to refer him for central auditory testing. As we may not be able to evaluate central auditory processing in the early childhood, identifying the possible (C)APD signs by a SLP may help them to plan a more suitable program even before reaching a definite diagnosis.