Audiology

Manufacturing sound absorber based on combined recycling of polyethylene trephetalat and polystyrene at low and median frequencies

Zeynolabedin Ghanbarzadeh Alamdari

Background and aim: Noise pollution is one of the main cause of occupational hearing loss. According to WHO reports in many countries workers have been exposed to 85 - 90 dB noise level. The purpose of this study is to manufacture a sound absorber based on combined recycled polyethylene trephetalat (PET) and polystyrene (PS) with an economical method in order to control of noise pollution
Materials and methods: Sound absorber were made of PET and PS with equal weight percent, polyester fiber, and polyvinyl acetate resine, with five to ten centimeters thick. Sound mean absorption coefficient percents were determined by acoustic impedance tube and compared with those of rock wool.
Results: Mean absorption coefficient percent of samples with one to five millimeter pore size and ten centimeters thickness was significantly better than those with six to twenty millimeters pore size in 50 to 630, 1250, and 1600 Hz, (p<0.05). In general, samples mean absorption coehicient was significally different from those rock wool (p=0.005).
Conclusion: Recycle polymere absorbers may play an important role in national economics as they are prophylactic to some occupational disease and also are economical.

Risk perception, knowledge and safety attitude and hearing protector use in petrochemical industry workers

Mahdi Jahangiri

Background and Aim: Hearing protectors (HP) are widely employed as the only measure against noise exposure. However, it is well known that unless do workers wear HP continuously, its efficacy will be very low. The purpose of this study was to determine the influence of risk perception, knowledge and safety attitude on hearing protection use in petrochemical industry&aposs workers.
Materials and Methods: In this cross-sectional study a structural questionnaire was administrated to 236 randomly selected workers in Iranian petrochemical industry who had been to 85 dBA noise and some influencing factors including risk perception, knowledge and general attitude to safety on using of HP had been investigated.
Results: This study showed that only 20.3% of employees claimed to wear hearing protection all the time when they exposed to noise. There was a significant relationship between use of hearing protector and worker&aposs risk perception (p=0.048) and also their knowledge about hearing protection(p=0.009). Also, the relationship between general attitude of workers to safety and risk perception was statistically significant (p=0.046).
Conclusion: The results of the study showed that for promoting the use of hearing protectors, two main strategy should be followed. First, removing the barriers to make hearing protectors compliant, and second enhancing the workers&apos risk perception about hearing loss and proper use of ear protectors.

Effectiveness of low level laser irradiation on tinnitus and parameters of electrocochleography and distortion product otoacoustic emissions

Saeed Mahmoudian

Background and Aim: Tinnitus is the consciousness of sound that arises in the ear or head without any external sound origin. The efficacies of transmeatal low-level laser irradiation for tinnitus treatment were reported before. The aim of this study was to evaluate the effectiveness of low level laser therapy on tinnitus and ECochG and DPOAEs parameters.
Materials and Methods: The study design was prospective, quasi experimental. This investigation conducted on 16 ears (10 patients) with disabling tinnitus. All patients underwent ENT examination, complete audiological evaluation, tinnitus study, ECochG and DPOAEs, and finally completing tinnitus data sheet. The results were compared before and after irradiation.
Results: Means of tinnitus loudness (LMT) and CAP amplitudes were significant different before and after irradiation (p<0.005). There was no any other significant difference before and after low level laser irradiation in subjective loudness, pitch matching annoyance grade of tinnitus and DPOAEs and other ECochG parameters.
Conclusion: Transmeatal low-power laser irradiation with 200 mW seems not to be effective for treatment of tinnitus. This paper is the research brief report. In clinical point of view, this study should be repeated with a greater sample size although our results were statistically important.

Identifying cochlear dead regions in hearing impaired children with the threshold equalizing noise test

Mina Milani

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 (TEN_HL) 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 forteen 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.

Survey of saccadic parameters using videonystagmography in patients with idiopathic Parkinson's disease and normal subjects

Abdorreza Sheibanizadeh

Background and Aim: Patients with Parkinson&aposs disease manifest oculomotor abnormalities. This is the consequence of basal ganglia impairment. The most common abnormalities include increased saccade latency, hypometric saccades and decreased saccade velocity. The purpose of this study was comparison of saccadic parameters using videonystagmography in patients with idiopathic Parkinson&aposs disease and normal subjects.
Materials and Methods: In this cross sectional study, saccadic movements were investigated in thirty patients with idiopathic Parkinson&aposs disease and thirty age matched subjects were 35-70 years old. Saccade latency, velocity and accuracy were quantitatively analyzed.
Results: Results of this study indicated increased saccade latency, reduction of saccade velocity and accuracy in patients with Parkinson&aposs disease(P<0.001).
Conclusion: This study showed that patients with Parkinson&aposs disease manifest saccadic deficits. This suggests dopaminergic control of these ocular movements.

Effects of caffeine on auditory brainstem response

Saeed Farahani

Background and Aim: Blocking of the adenosine receptor in central nervous system by caffeine can lead to increasing the level of neurotransmitters like glutamate. As the adenosine receptors are present in almost all brain areas like central auditory pathway, it seems caffeine can change conduction in this way. The purpose of this study was to evaluate the effects of caffeine on latency and amplitude of auditory brainstem response(ABR).
Materials and Methods: In this clinical trial study 43 normal 18-25 years old male students were participated. The subjects consumed 0, 2 and 3 mg/kg BW caffeine in three different sessions. Auditory brainstem responses were recorded before and 30 minute after caffeine consumption. The results were analyzed by Friedman and Wilcoxone test to assess the effects of caffeine on auditory brainstem response.
Results: Compared to control group the latencies of waves III,V and I-V interpeak interval of the cases decreased significantly after 2 and 3mg/kg BW caffeine consumption. Wave I latency significantly decreased after 3mg/kg BW caffeine consumption(p<0.01).
Conclusion: Increasing of the glutamate level resulted from the adenosine receptor blocking brings about changes in conduction in the central auditory pathway.

A comparison of thresholds in auditory steady - state response with pure tone audiometry in subjects with normal hearing and those with mild and moderate sensorineural hearing loss

Sadegh Jafarzadeh

Background and Aim: Among all auditory assessment tools, auditory steady state response (ASSR) is a modern test. Modulation frequency for this test is usually 80 Hz. The purpose of this study, was to examined adult subjects with 40 Hz and 80 Hz ASSR and compare the results.
Materials and Methods: Thirty adult (60 ears) were evaluated by ASSR and PTA test, Results were divided into three groups: normal hearing, mild and moderate sensorineural hearing loss.
Results: In all groups, forty hertz ASSR thresholds were relatively closer to behavioral threshold than those of 80 Hz ASSR(p<0.05). Besides, the more severe hearing loss, the lower the difference between those two thresholds. Correlation coefficients were also higher in 40 Hz ASSR(p<0.05).
Conclusion: Frequency modulation thresholds with 40 Hz are more likely to be closer to the behavioral thresholds. Moreover, it has better results than the thresholds with 80 Hz.

Standardization of maximum phonation time among the guidance students in Tehran

Mohammad Rahim Shahbodaghi

Background and Aim: The primary energy for speech production is prepared by breathing flow. As there was no index for the maximum phonation time(MPT) to compare normal and speech disordered speakers in Iran, the purpose of this study was to establish this standard for guidance school students in Tehran.
Materials and Methods: This cross-sectional study was performed on 576 guidance students from 1^st, 5^th, 8^th, 10^th, 15^th and 19^th educational regions. Each student made an usual inhalation and produced the /a/ for three times with the maximum strength but in a way that he/she didn&apost feel tension on his/her neck or larynx. The maximum time was recorded as the maximum phonation time.
Results: The results of this research revealed that girls`s MPT in all regions was 15.3, 16.7, and 17.16 seconds and the boys` was 15.41, 16.7 and 17.01 seconds and all students` 15.36, 16.17 and 17.08 seconds in order of their grades. There was significant difference between first and third grade mean MPT (p=0.003).
Conclusion: The result of this study indicates that, as the students age increases their MPT increase, too. Also, boys` MPT was more than girls` in first and second grades however, in third grade the girls` MPT was more.