Introduction: Cochlear dead zones are defined as areas where the inner hair cells have been destroyed.Thresholds on the audiograms show the integrity of those parts of the ear that are tested. Care must be taken in interpretating audiograms. Thanks to the advances in understanding of cochlear functions, it is now possible to spot false responses that come from dead zones of the cochlea. Recently, cochlear dead regions have been detected via TEN (Threshold Equalizing Noise) test in which ipsilateral broadband noise and threshold shifting are used.Materials and Methods: A review of the literature on the subject of dead zones published from 1993 to 2003 was performed using Pubmed, Ebsco, Science Direct, Google Scholar Thieme ProQuest databases and library sources. key word: were "cochlear dead zone", "traveling wave", "TEN (threshold equalizing noise) test", "ipsilateral noise" and "real-ear measurement for hearing aids prescription".Conclusion: Hearing aids fitting process for patients with severe and sloping sensory neural hearing loss must be noted specially by amplifying active zone and avoiding amplification for dead region i.e., offering amplification to the transition frequencies that have better hearing than others, those among the fine regions and the dead zones. Dead zone detection may help in hearing aids fitting and fine tuning.

Background and Aim: Regions in the cochlea with no (or very few) functioning inner hair cells and/or neurons are called dead regions. The aim of this study was to identify the cochlear dead regions in moderate to profound sensory neural hearing impaired children through the Threshold equalizing noise (TENHL) test.Materials and Methods: In this cross-sectional study, the TEN (HL) was performed for the all frequencies available on test CD, on 30 children with ages ranging from five to fourteen years (mean age, 8.5±2.8 years old).Results: In this study, 58.3% of ears were found to have a dead region for at least one frequency. Classifying by test frequencies, 20% were found to have a dead region, 24% to be inconclusive and 56% to have no dead regions. The difference between mean SNR (T) in ears with and without dead regions was statistically significant. The difference between mean absolute thresholds in two groups was statistically significant at 1000 Hz and below (p<0.05).Conclusion: The results indicated a relatively high prevalence of dead regions in children with sensory neural hearing impairment, especially for frequencies at which the hearing loss exceeds 70 dB HL.

Background and Aim: Hearing loss is one of the most common disorders in the elderly people. Sensory neural hearing loss mostly results from outer and inner hair cell damages in cochlea. The area wherein inner hair cells or auditory nerve fibers are inactive is named Dead Region (DR) or Cochlear dead Region (CDR). Many studies have investigated DR at high frequencies in sloping or sharply sloping audiograms, but few studies have investigated flat audiograms. Hence, the aim of the present study was to investigate the prevalence of DR in hearing impaired adults with mild to severe flat sensory neural hearing loss. Materials and Methods: In the current descriptive-analytical study, 30 elderly people (60 ears) aged 65 years and above, with bilateral mild to severe flat sensory neural hearing loss were tested for DR at frequencies from 0. 5 to 4 kHz using the threshold equalizing noise (HL) test. Based on the hearing thresholds, participants were divided into three groups of mild, moderate, and severe hearing loss. Results: The prevalence of DR at 2 kHz, 3 kHz, and 4 kHz were significantly higher than DR at frequencies below 2 kHz (p<0. 05). With increasing the amount of hearing loss, the number of DR increased. As a result, the difference between prevalence of DR in severe hearing loss and the other two groups was statistically significant (p<0. 05). Conclusion: The results indicated a relatively high prevalence of dead regions in the elderly with severe degree of hearing loss (60-80dBHL) and at high frequencies. Furthermore, with increasing frequency, the number of dead regions increased correspondingly.

In recent years substantial numbers of econometric papers have addressed estimation and inference methods of the Threshold Auto Regression model. Threshold Auto regression model are able to capture asymmetric and nonlinear movement of variables. This paper explains the characteristics of threshold models and some different applications of these models and then, investigates the threshold auto regression models and momentum threshold auto regression models. Finally, presenting some examples of threshold models, we used the threshold co Integration test advanced by Enders and Siklos (2001) to investigate the asymmetric adjustment on long-run (PPP) in Iran between 1339 and 1390. Results prove PPP theory and imply that the adjustment process towards long run PPP is asymmetric.

Background and Aim: Acceptable noise level (ANL) is the loudest level of background noise that human can tolerate while lisTENing a running speech. ANL test is used for the prediction that whether a hearing aid (HA) candidate can use HA successfully by determining how well the individual tolerates background noise while lisTENing to speech. In the current review, we reviewed the basis and theories of the ANL test and the factors that identified from the studies that have conducted on ANL and the influence of this test in increasing the quality of life of hearing aid users along with a discussion of its application in clinical audiology.Recent Findings: Research showed that subjects with a higher tolerance for background noise are most probable to be the successful hearing aid users. Clinical trials demonstrated that ANL test provides reliable results and can predict HA successful use with 85% accuracy.Conclusion: Acceptable noise level is a reliable and valid test that can be used as a predictive index for the successful application of HA, and it is applicable in before/after HA fitting assessments.Thus, it is suggested that ANL can be implemented in the fitting and counseling process of HAs prescription. Further studies are required to resolve biases over the employment of this test in bilinguals.

It has been shown that many types of physical - environmental stresses during fetal life alter behavioral responses to stimuli. Sex hormones have been shown to be evolved in these behaviors. Nociception can also be affected by stress, but the mechanism (s) are not fully investigated. In this study NMRI pregnant rats (220-250 gr) were exposed to repetitive one hour intermitTENt noise stress (90-120 db, low frequency, white noise) during night dark cycle. InTENsity and frequency of noise varied each 2-3 minutes between minimum and maximum levels. Pain thershold was measured after after subcutaneous injection of 50 ul  formalin (2.5%) in right paw. The experimentmsubcutaneous injection of 50 considered to have two stages: 1) phasic pain, minutes 0-15 and 2) tonic pain minutes 20-50. Pain score was marked every 15 seconds. The results showed that exposing to noise stress during fetal life has mostly affected tonic pain threshold. Pain threshold in stressed female offspring was increased significantly compared to stressed male offspring or compared to control male and female offspring. In conclusion it is suggested that noise stress during fetal life may increase pain threshold (hypoalgesia). Increase in endogenouse opioid release may be considered as the mechanism.

Background and Aim: Quick Speech in Noise (Q-SIN) test has popularity for evaluating speech recognition in noise. The present study has been paid to build five new Persian lists with respect to all possible factors affecting the test, to determine validity of the test and to run five lists for normal hearing subjects and assessment of reliability.Methods: To build lists, frequent, familiar and difficult in terms of cognitive (cohort size of above three) words were used to construct unpredictable senTENces. After determining the conTENt and face validity, the 30 selected senTENces were recorded in the studio by a familiar female speaker. The recorded senTENces and prepared four talker babbling noise were combined in Cool Edit software. Then five test lists were conducted in 35, 18-35 year old individuals with normal hearing. The reliability was assessed with the retest after two weeks.Results: The 30 senTENces became valid (conTENt and face validity) with the change according to expert judges. The average Signal to noise ratio (SNR) loss of five lists was 0.35 dB. There was no significant difference between men and women in all lists except list 4 (p=0.03). The results indicate no difference in the average SNR loss between five Lists. In reliability assessment test-retest correlation coefficient was 8.0 (p<0.05). Intra-class coefficient (ICC) for lists was statistically significant (p=0.00) and confirmed the lists have reliability and high repeatability.Conclusions: The Developed lists are valid, equivalent and reliable and can be utilized in clinical application.

2Introduction: Noise exposure may cause a kind of sensorineural hearing loss. Noise-induced hearing loss is known as an occupational disease, but the effect of exposure to recreational noise is not completely understood. This study aimed to assess the impact of exposure to recreational noise on hearing status. Materials and Methods: This was a cross-sectional study of 304 medical students. The participants were randomly selected from medical students in years 4 to 6 and were divided into two groups regarding their exposure to recreational noise. Conventional audiometry was done for all participants, and hearing thresholds at different frequencies were compared between two groups. Data were analyzed using SPSS (ver. 20) using Kolmogorov-Smirnov, Mann-Whitney U, and chi-square tests. Results: The mean age of the participants was 23.18±3.14 years. In total, 74.7% of participants were exposed to recreational noise. The mean duration of noise exposure was 4.67±2.91 years. The most frequent exposure was to music via a headphone or hands-free (27.3%). All hearing thresholds in both groups were within the normal range and there was no significant difference between the two groups regarding hearing thresholds. Conclusion: The results of the present study showed that any exposure type of recreational noise (music, eulogy, or lecture) in the young population did not affect hearing thresholds.