Studies Of Noise-induced Hearing Loss Research Articles

The Monitoring Environmental noise in Coffee Production, CCT/NCBA Companies in Bidau Lesidere Villige, Dili District Dili City Timor Leste

Noise-induced hearing loss is hearing loss caused by exposure to quite loud noise over a long period of time and is usually caused by noise in the work environment, in this case the company environment. Working environment noise is a major problem in occupational health which is a standard of OSH in various companies, the relationship between excessive noise exposure and hearing loss has been known since ancient times. Various epidemiological studies of noise-induced hearing loss have explored the relationship or risk factors between work, exposure to noise levels and the degree of hearing loss. The purpose of this study was to determine and survey the noise of electronic machines on hearing loss. The research method used is a quantitative, observational method using a cross observational study design.

Integrating pharmacogenomics into clinical trials of hearing disorders.

In 2019, the U.S. Food and Drug Administration issued guidance to increase the efficiency of drug development and support precision medicine, including tailoring treatments to those patients who will benefit based on genetic variation even in the absence of a documented mechanism of action. Although multiple advancements have been made in the field of pharmacogenetics (PGx) for other disease conditions, there are no approved PGx guidelines in the treatment of hearing disorders. In studies of noise-induced hearing loss (NIHL), some progress has been made in the last several years associating genomic loci with susceptibility to noise damage. However, the power of such studies is limited as the underlying physiological responses may vary considerably among the patient populations. Here, we have summarized previous animal studies to argue that NIHL subtyping is a promising strategy to increase the granularity of audiological assessments. By coupling this enhanced phenotyping capability with genetic association studies, we suggest that drug efficacy will be better predicted, increasing the likelihood of success in clinical trials when populations are stratified based on genetic variation or designed with multidrug combinations to reach a broader segment of individuals suffering or at risk from NIHL.

Temporary Hearing Threshold Shift in California Sea Lions (Zalophus californianus) Due to One-Sixth-Octave Noise Bands Centered at 2 and 4 kHz: Effect of Duty Cycle and Testing the Equal-Energy Hypothesis

In one of a series of studies of noise-induced hearing loss to determine the frequency-dependent susceptibility of California sea lions (Zalophus califor-nianus) to temporary hearing threshold shift (TTS), two subjects were exposed for 60 min to two different fatiguing sounds. These were continuous one-sixth-octave noise bands (NBs), centered at 2 kHz, at sound pressure levels (SPLs) of 138 to 167 dB re 1 µPa (resulting in sound exposure levels [SELs] of 174 to 203 dB re 1 µPas), and at 4 kHz, at SPLs of 133 to 169 dB re 1 µPa (resulting in SELs of 169 to 205 dB re 1 µPas). Using a psychoacoustic technique, TTSs were quantified at 2,2.8,4.2,5.6, and 8 kHz (at the center frequency of each NB, at half an octave higher, and at one octave higher). After exposure to both NBs, higher SELs resulted in greater TTS at all healing frequencies that were tested. TTSs and healing recovery patterns were similar in both sea lions. The effect of fatiguing sound duty cycle on TTS was investigated with the NB at 4 kHz and with 1.6-s signal duration, at a mean SPL of 169 dB re 1 µPa. Duty cycle reduction from 100 to 90% resulted in the largest decrease in TTS, and no TTS occurred at duty cycles ≤ 60%. The equal-energy hypothesis was investigated with the NB at 4 kHz: five combinations of SPL and exposure duration that resulted in the same SEL (197 dB re 1 µPas) produced similar initial TTSs in both sea lions. Susceptibility of California sea lions to TTS is higher than previously believed; for sounds around 2 and 4 kHz, it is similar to the susceptibility of harbor seals (Phoca vitulina). These data will contribute towards the development of an evidence-based underwater sound weighting function for the protection of Otariidae.

Long-term evidence of noise-induced permanent threshold shift in a harbor seal (Phoca vitulina).

In psychophysical studies of noise-induced hearing loss with marine mammals, exposure conditions are often titrated from levels of no effect to those that induce significant but recoverable loss of auditory sensitivity [temporary threshold shift (TTS)]. To examine TTS from mid-frequency noise, a harbor seal was exposed to a 4.1-kHz underwater tone that was incrementally increased in sound pressure level (SPL) and duration. The seal's hearing was evaluated at the exposure frequency and one-half octave higher (5.8 kHz) to identify the noise parameters associated with TTS onset. No reliable TTS was measured with increasing sound exposure level until the second exposure to a 60-s fatiguing tone of 181 dB re 1 μPa SPL (sound exposure level 199 dB re 1 μPa2s), after which an unexpectedly large threshold shift (>47 dB) was observed. While hearing at 4.1 kHz recovered within 48 h, there was a permanent threshold shift of at least 8 dB at 5.8 kHz. This hearing loss was evident for more than ten years. Furthermore, a residual threshold shift of 11 dB was detected one octave above the tonal exposure, at 8.2 kHz. This hearing loss persisted for more than two years prior to full recovery.

Noise Induced Hearing Loss (NIHL) Effect among Workers in Small Medium Enterprises (SME) in Malaysia

A cross-sectional study of noise-induced hearing loss (NIHL) due to occupational noise exposure of greater than 90 dB (A) was conducted among Small Medium Enterprise (SMEs) workers throughout Malaysia. Area noise monitoring was carried out to determine the high risk area exposed to noise. Personal noise monitoring was conducted among the exposed workers. Questionnaire on demographic information including medical history was obtained. The secondary data on individual audiometric assessment was obtained from 18 SMEs. There are 5 out of 18 SMEs in this project with the measured area noise level greater than 90 dB(A) - this is not in compliance with the Factories and Machinery Act 1967 (Noise Regulation 1989). This study revealed that there was a significant correlation (r = 0.469, p = 0.003) between area noise monitoring and personal noise monitoring. Furthermore, there were complaints on sudden hearing loss, ear pain and ringing sound in ears received from the workers.

Sex bias in basic and preclinical noise-induced hearing loss research.

Introduction:Sex differences in brain biochemistry, physiology, structure, and function have been gaining increasing attention in the scientific community. Males and females can have different responses to medications, diseases, and environmental variables. A small number of the approximately 7500 studies of noise-induced hearing loss (NIHL) have identified sex differences, but the mechanisms and characterization of these differences have not been thoroughly studied. The National Institutes of Health (NIH) issued a mandate in 2015 to include sex as a biological variable in all NIH-funded research beginning in January 2016.Materials and Methods:In the present study, the representation of sex as a biological variable in preclinical and basic studies of NIHL was quantified for a 5-year period from January 2011 to December 2015 prior to the implementation of the NIH mandate.Results:The analysis of 210 basic and preclinical studies showed that when sex is specified, experiments are predominantly performed on male animals.Discussion:This bias is present in studies completed in the United States and foreign institutions, and the proportion of studies using only male participants has actually increased over the 5-year period examined.Conclusion:These results underscore the need to invest resources in studying NIHL in both sexes to better understand how sex shapes the outcomes and to optimize treatment and prevention strategies.

Validation of Reference Genes for RT-qPCR Analysis in Noise-Induced Hearing Loss: A Study in Wistar Rat.

The reverse transcriptase–quantitative polymerase chain reaction (RT–qPCR) requires adequate normalization in order to ensure accurate results. The use of reference genes is the most common method to normalize RT–qPCR assays; however, many studies have reported that the expression of frequently used reference genes is more variable than expected, depending on experimental conditions. Consequently, proper validation of the stability of reference genes is an essential step when performing new gene expression studies. Despite the fact that RT–qPCR has been widely used to elucidate molecular correlates of noise–induced hearing loss (NIHL), up to date there are no reports demonstrating validation of reference genes for the evaluation of changes in gene expression after NIHL. Therefore, in this study we evaluated the expression of some commonly used reference genes (Arbp, b–Act, b2m, CyA, Gapdh, Hprt1, Tbp, Tfrc and UbC) and examined their suitability as endogenous control genes for RT–qPCR analysis in the adult Wistar rat in response to NIHL. Four groups of rats were noise–exposed to generate permanent cochlear damage. Cochleae were collected at different time points after noise exposure and the expression level of candidate reference genes was evaluated by RT–qPCR using geNorm, NormFinder and BestKeeper software to determine expression stability. The three independent applications revealed Tbp as the most stably expressed reference gene. We also suggest a group of top–ranked reference genes that can be combined to obtain suitable reference gene pairs for the evaluation of the effects of noise on gene expression in the cochlea. These findings provide essential basis for further RT–qPCR analysis in studies of NIHL using Wistar rats as animal model.

The prevalence of noise-induced hearing loss among Tanzanian miners

BackgroundTanzania has a young mining history with several operating open pit and underground mines. No prevalence studies of noise-induced hearing loss (NIHL) have been conducted among mine workers to provide an impetus for the development of comprehensive hearing protection programmes.AimsTo determine the prevalence of NIHL and associated factors among miners in a major gold mining company operating in Tanzania. Associated risk factors such as age, sex and duration of exposure were examined.MethodsAudiograms obtained from periodic medical examinations were categorized using the UK Health & Safety Executive system.ResultsA total of 246 audiograms were studied. The prevalence of NIHL was 47%, with 12% with poor hearing and 35% with mild hearing impairment. The proportion of NIHL increased with total years of exposure to noise. Underground miners were more affected (71%) than open pit miners (28%). These findings were statistically significant. The highest proportion of miners with NIHL (60%) was among the youngest age group (20–29 years).ConclusionsThere was a high prevalence of NIHL in the company under study. There was a strong correlation with type of mining, age and years of exposure. The findings have been used to develop comprehensive hearing conservation programmes.

An outbreak of listeriosis in a breeding colony of chinchillas.

Listeria monocytogenes is a facultatively anaerobic short gram-positive rod-shaped bacterium that infects a wide range of animals, including ruminants, monogastric animals, birds, fish, rodents, and humans. Infection with this obligate intracellular pathogen causes 3 distinct clinical entities, septicemia, encephalitis, and abortion, which rarely occur simultaneously in the same animal. The septicemic form affects the viscera with or without meningoencephalitis and is common in monogastric animals, whereas encephalitis and abortion occur principally in adult ruminants. Chinchillas are considered one of the species more susceptible to visceral listeriosis, especially when reared in confinement. Listeriosis in chinchillas has been described in many areas of the United States during a period (1949-1955) when chinchilla pelts were prized commodities in the fur industry. More recently, chinchillas have become a widely used animal model for studies of noise-induced hearing loss. An outbreak of disseminated visceral listeriosis occurred in a breeding colony of 130 chinchillas located in northern Idaho. The chinchillas in this operation were raised for pelts. Polygamous breeding was practiced; 1 male had access to 8 females. The feed, open sacks of commercially formulated chinchilla pellets and a bale of hay, was stored on a wood pallet. To promote maintenance of their hair coats, a dust bath pan was provided for the animals. During December 1995, there was an unusually large influx of mice into the chinchilla building, and on several occasions the owners noted mouse droppings in the feed. By January 1996, the colony experienced a 23% mortality (30 of 130) in breeding animals of various ages. Approximately 4 days prior to death, the animals were anorectic and hunched, and some had torticollis. Many animals were found dead without premonitory clinical signs. Four chinchillas (2 dead males, 1 dead female, 1 moribund female) were submitted to the Washington Animal Disease Diagnostic Laboratory for necropsy. All 4 chinchillas were emaciated and lacked subcutaneous and retroperitoneal fat. Consistent gross lesions in the 3 dead chinchillas included multifocal 0.1-0.3-cm-diameter whitetan foci affecting the capsular surfaces and parenchyma of the liver, mesenteric lymph nodes, and the serosa of the small and large intestines, particularly the cecum and colon. Individual differences in postmortem lesions are listed in Table 1. Animal A, a dead female, had a 2-cm rectal prolapse and colonic intussusception in addition to the visceral foci. The intussusception consisted of a 3-cm segment of dark red prox-

Women with noise-induced hearing-loss: an invisible group?

The aim of this qualitative study was to describe, from the perspective of women with noise-induced hearing loss (NIHL), their experiences of noise as a threat to health and their having to live with a hearing disability, i.e. behaviours, thoughts and emotions in auditory demanding situations. Ten women, patients with NIHL at the Department of Audiology, Borás' Hospital in Sweden, were selected to form a heterogeneous sample. A taped in-depth interview, lasting from 45 minutes to 1 hour, was conducted with each woman. The verbatim transcribed interviews were consecutively analysed using a method influenced by the tradition of grounded theory. Four categories emerged in the process of analysis. These categories were labelled: lack of awareness, ambivalence, controlling and avoiding coping strategies and stigmatization. The category 'lack of awareness' concerned the women's perceptions of the risks of noise on hearing, the lack of efforts on the part of the women to apply for financial compensation for their NIHL, the lack of an awareness of individual's right to have healthy work-place and to receive professional help for hearing impairment. Also lacking was the concept that hearing impaired individuals have the right to participate in the community on similar conditions as non-hearing impaired people. This lack of awareness was identified as a core category relating to the other categories: ambivalence, controlling and avoiding coping strategies and stigmatization. The women's expressions indicated ambivalence concerning the cause of the hearing disability and, also, how to manage the consequences of it: the women in the study seemed to alternate between feelings of hopelessness/resignation and a state of acceptance of the hearing disability. Furthermore, the women alternated between blaming themselves and blaming others for the cause of the hearing loss, indicating a change between internal and external locus of control. Also, the women alternated between controlling and avoiding strategies in coping with demanding auditory situations. The coping strategy chosen by the women in a specific situation intended to prevent or minimize stigmatization, i.e. 'to pass as normal' and thereby to maintain a positive self-image of normality. Despite this, the women often perceived negative and stigmatizing attitudes from others, which reinforced their feelings of ambivalence in how to manage the situation. The hypothesis based on the present pilot study, that women with NIHL are more likely to pass themselves off as normal hearing and therefore might be less likely to be reported in studies of NIHL than men, needs to be further tested in a larger sample.

A study of noise-induced hearing loss and blood pressure in steel mill workers.

A cross-sectional study on noise-induced hearing loss and blood pressure was conducted in a steel mill company. Three hundred testees were selected by cluster sampling. They were physically examined and an audiometry was done. Only 151 workers, who had the highest hearing threshold at 4000 Hz and without any family history of hypertension or treatment of drugs on cardiovascular troubles, were selected as subjects in this study. Multiple regression analyses revealed that body mass index, employment duration, age and hearing loss explained a significant amount of variation in systolic and diastolic blood pressure (R2 = 0.16 and 0.12, respectively). There was no significant relationship between hearing loss and blood pressure. In order to adjust confounding factors, analyses of covariances were used and the results suggest that hearing loss is unrelated to blood pressure. It seems that hearing loss is not appropriate as a noise exposure index to measure the relationship between noise exposure and blood pressure.

Behavioral studies of noise-induced hearing loss in primates: loudness recruitment.

Behavioral studies of noise-induced hearing loss in primates: loudness recruitment.

PREDICTING HEARING LOSS FROM NOISE-INDUCED TTS.

Introduction IN 1961 the Research Center of the Subcommittee on Noise initiated a longitudinal (field) study of noise-induced hearing loss. Industrial environments were selected which provided a continuous, unvarying noise with intensities about 75 db sound pressure level (SPL) in the octave bands falling between 300 cps and 4,800 cps. Individuals who worked in these noise environments were chosen for study using the following criteria: (1) no history of habitual exposure to noises other than those found in their present environment, (2) no history of otologic disease, (3) no evidence of existing otologic malfunction, and (4) no habitual exposures to the present noise environment longer than ten years. Threshold tests were made on the individuals so selected at 1,000, 2,000, 3,000, and 4,000 cps. The testing procedure and apparatus have been previously described. 1 All threshold testing was done in a mobile unit containing an Industrial Acoustics Model 401 test