Frequency-Based Analysis of Auditory Threshold Shifts Induced by Noise Color in Rats

Introduction: Colored noises with acoustic and psychoacoustic characteristics have several biological effects on human or animal health. While studies on auditory effects focus on noise’s physical aspects, its psychoacoustic aspects can also result in health and safety risks. Therefore, this study aims to investigate frequency-based damages due to exposure to colored noise in an animal model. Material and Methods: Twenty-four male Wistar rats were randomly divided into four groups (6 in each group). The groups included the control (no exposure) and three exposure groups (white, pink, and violet). The rats were exposed to 110 dB SPL for 4 hr/day for 14 consecutive days. Auditory brainstem responses (ABR) with click and tone-burst stimuli were recorded one day before (baseline), 7, and 14 days after exposure. Statistical analyses were conducted using ANOVA and repeated measures ANOVA. Results: There was a statistically significant increase in ABR threshold values in exposure groups (p<0.05). Hearing threshold shifts in the white noise group showed a homogeneous pattern, violet noise showed an increasing pattern, and pink noise showed a decreasing pattern in low frequencies and a homogeneous pattern with increasing frequency. The highest shift in hearing threshold was observed in exposure groups from day 0 to 14. Additionally, the shift in hearing threshold in the second week was less than in the first one. Conclusion: The current study observed that noise’s power spectral density affected hair cells’ damage severity. Accordingly, pink noise causes less damage to the cochlea compared to white and violet. Over time after noise exposure, cochlear pathogenesis gradually decreases and hair cell lesions become stable

The Relationship between Occupational Noise Exposure and Noise Induced Hearing Loss (NIHL) in Small-Scale Industries: A Case Study in the City of Damavand, Iran

Background: Exposure to the excessive levels of occupational noise is one of the principal harmful agents affecting the workers’ health. This study aimed to investigate the relationship between the occupational noise exposure and the hearing loss caused by working in small-scale service industries in the city of Damavand, close to the metropolitan capital city of Tehran, Iran. Methods: This descriptive cross-sectional study investigated the occupational noise levels within the 90 small-scale industries (mainly service industries and workshops) working under the supervision of Damavand healthcare network governed by the Iranian ministry of health and medical education. A sound level meter (Bruel and Kjær 2250) was employed to determine the noise exposure levels based on the dB A, and according to the standard ISO 9612: 2009. The audiometric exam tests were performed by an audiometer (model MEVOX SA-900). The obtained data were then analysed by SPSS 16, using linear regression and t-test. Results: The highest measured 8-hour equivalent continuous sound pressure levels (Leqs) were associated with auto body mechanics (89.2 dB A), foundry and casting workers (88.8 dB A), aluminium products fabrication workers (86.32 dB A), blacksmiths and forging (85.8 dB A) carpenters (84.93 dB A), and cabinet manufacturers, respectively (84 dB A). Results from the hearing threshold shifts of the workers from the studied occupational groups revealed that the highest work related hearing loss associated with the right ear occurred among the auto body mechanics, aluminium products fabrication workers and carpenters. However, the most significant work-related hearing loss associated with the left ear was noticed among carpenters, aluminium products fabrication workers, and auto body mechanics, respectively. Pearson correlation coefficient was tested between Leqs, work experience and hearing loss, and the results implied that the progress of workers’ hearing loss was correlated with the increase in work history and experience. Conclusions: The 8-hour Leqs and work experience were, respectively, the most important factors affecting the rate of hearing loss among the participants of this study. Keywords: Noise-Induced Hearing Loss, Sound Pressure Level, Small-Scale Industrie

The Identification of Respiratory and Hearing Protection Equipment Selection Criteria:A Cross-Sectional Study in Tehran Industries

Introduction: To ensure employee safety and health, it is crucial to choose and use personal protective equipment correctly. An investigation of the respiratory and hearing protection equipment used in the industries of Tehran was conducted in the present study. Material and Methods: This study was a descriptive-analytical study conducted in 2023 on 400 occupational health and safety experts in Tehran province. A researcher-made checklist and questionnaire (physical and online versions) were used to determine the criteria that are considered when selecting protective equipment. Statistical analysis and graphing were performed using SPSS-v21 and Excel-2016. Results: Participants had an average age of 38.66 and an average work experience of 11.78 years. The participants reported 48.3% and 47.7% disapproval of the quality and 42.5% and 39.5% disapproval respectively of the quantity of respiratory and hearing protection equipment available in their industrial units. In addition, 56.3% of them admitted that they have no responsibility for providing or approving the equipment in their workplace. Overall, 27 and 29 criteria were mentioned by study participants pertaining to respiratory and hearing protection equipment, respectively. In the identified criteria, the frequency distribution ranged from 0.3% to 38%. Conclusion: A high rate of expert dissatisfaction with protective equipment and a low frequency of most of the criteria mentioned indicates that industries aren’t paying much attention to the issue of choosing the right respiratory and hearing protection equipment. To improve the situation, more investigation is needed and practical and operational solutions will be provided. This study highlights the importance of proper selection and use of personal protective equipment in ensuring the safety and health of employees.</p

اثرات صدای بنفش بر روی میزان بیان ژن SLC26A4در بافت حلزون گوش رت

Background and Aims: As one of the most important physical detrimental factors, purple noise can be considered similar to sounds that a wide range of people are exposed to in their workplaces. Also, cochlear tissue samples are the best tissue samples to evaluate gene expression and pathologic studies following noise exposure. Therefore, the aim of this study was to investigate the effects of purple noise on the expression of SLC26A4 gene in cochlear tissue. Methods &amp; material: Totally, 10 male Wistar rats were used in this experimental study. Both N1 and N2 exposure groups were exposed to purple noise with sound pressure level of 115-120 dB and frequency range of 4-20 kHz. Histological tests were performed for pathological studies. Finally, the relative expression of SLC26A4 gene was determined by qRT-PCR technique. All experiments were conducted according to ethical standards of working with laboratory animals. Results: The results showed that the expression of SLC26A4 gene decreased significantly compared to the normal level in both N1 and N2 groups. The results of cochlear tissue pathology showed that the group exposed to purple noise for 6 days had more mechanical damage 7 days after cessation of exposure. Conclusion: Significant decreased expression in SLC26A4 gene and permanent damage to the Reissner and Basal lamina membranes in the cochlear tissue and the auditory nerve ganglion leads to strengthening the incidence of advancing sensorineural hearing impairment and increases the likelihood of metastasis in cochlear tissue.زمینه و اهداف: صدای بنفش را می­توان مشابه اصواتی در نظر گرفت که طیف وسیعی از افراد به عنوان یکی از مهم­ترین عوامل فیزیکی زیان­ آور، در محیط­های کاری خود در تماس با آن هستند. از طرفی، نمونه­ی بافت حلزون گوش بهترین نمونه بافتی جهت بررسی میزان بیان ژن­ و مطالعات آسیب شناسی، پس از تماس با اصوات محسوب می­شوند لذا هدف از این پژوهش، بررسی اثرات صدای بنفش بر روی میزان بیان ژن &nbsp;SLC26A4در بافت حلزون گوش بود. &nbsp; مواد و روش­ها: در مجموع، 10 سر رت نر با نژاد ویستار در این مطالعه تجربی استفاده گردید. دو گروه مواجههN1 &nbsp;و N2 در تماس با صدای بنفش (kHz20-4، dB120-115=SPL) قرار گرفتند. آزمایشات بافت شناسی جهت مطالعات آسیب شناسی بافت صورت گرفت و در پایان، میزان بیان نسبی ژن SLC26A4 بوسیله ی qRT-PCR تعیین گردید. کلیه آزمایشات این مطالعه، طبق موازین اخلاقی کار با حیوانات آزمایشگاهی انجام گرفت. &nbsp; یافته ها: نتایج نشان داد که در هر دو گروه مواجهه N1 و N2 کاهش معنادار میزان بیان ژن SLC26A4 نسبت به سطح نرمال اتفاق افتاده است. نتایج مطالعه­ی آسیب­ شناسی بافت حلزون گوش نشان داد که نمونه ی گروهی که 6 روز با صدای بنفش مواجهه داشت، پس از 7روز از قطع مواجهه صدمات مکانیکی بیشتری دیده بود. &nbsp; نتیجه­گیری: این سطح از کاهش بیان در ژن SLC26A4 و آسیب دائمی غشای رایسنر و بازال لامینا در بافت حلزون گوش و گانگلیون عصب شنوایی، منجر به تقویت بروز نقص شنوایی حسی-عصبی پیش رونده و افزایش احتمال متاستاز در بافت حلزون گوش می­گردد