The impact of hearing impairment and noise-induced hearing injury on quality of life in the active-duty military population:challenges to the study of this issue

The objectives of this review were to 1)summarize the available evidence on the impact of hearing loss on quality of life(QOL)among U.S.active-duty service members,2)describe the QOL instruments that have been used to quantify the impact of hearing loss on quality of life,3)examine national population-level secondary databases and report on their utility for studying the impact of hearing loss on QOL among active-duty service members,and 4)provide recommendations for future studies that seek to quantify the impact of hearing loss in this population.There is a lack of literature that addresses the intersection of hearing impairment,the military population,and quality of life measures.For audiological research,U.S.military personnel offer a unique research population,as they are exposed to noise levels and blast environments that are highly unusual in civilian work settings and can serve as a model population for studying the impact on QOL associated with these conditions.This review recommends conducting a study on the active-duty service member population using a measurement instrument suitable for determining decreases in QOL specifically due to hearing loss.

Evaluation of Digits-in-Noise Test and Hearing Handicap Inventory for Adults Screening in Patients with Occupational Noise-Induced Hearing Loss

Objective:To explore the clinical evaluation role of the Digits-in-Noise(DIN)test and Hearing Handicap Inventory for Adults Screening(HHIA-S)for patients with occupational noise-induced hearing loss and to observe and analyze their application values.Methods:Fifty patients with suspected occupational noise-induced hearing loss were randomly selected from the Department of Otolaryngology at the hospital as the research target.The collection period for the research cases spanned from January 2022 to November 2023,and all patients had a history of noise exposure.The DIN test and HHIA-S were used for hearing examinations,with clinical,comprehensive diagnosis serving as the gold standard to study their diagnostic performance.Results:The compliance rate of the DIN test was 88.00%,the HHIA-S’s compliance rate was 80.00%,and the combined compliance rate was 94.00%.The compliance rate of the DIN test and the combined compliance rates of the patients were statistically significant compared to the clinical gold standard data(P<0.05),while there was no difference between the compliance rate of the HHIA-S and the gold standard(P>0.05).The data shows that the sensitivity of the combined diagnosis is significantly higher than the sensitivity data of the DIN test and HHIA-S examination alone(P<0.05).Its specificity is 100.00%,and the accuracy data of the joint diagnosis in the degree were higher than those of the DIN test alone(P>0.05)and the HHIA-S alone(P<0.05).Conclusion:For patients with occupational noise-induced hearing loss,the joint evaluation of the DIN test and HHIA-S can significantly improve their diagnostic value with high sensitivity and accuracy.

Tranylcypromine upregulates Sestrin 2 expression to ameliorate NLRP3-related noise-induced hearing loss

Noise-induced hearing loss is the primary non-genetic factor contributing to auditory dysfunction.However,there are currently no effective pharmacological interventions for patients with noise-induced hearing loss.Here,we present evidence suggesting that the lysine-specific demethylase 1 inhibitor–tranylcypromine is an otoprotective agent that could be used to treat noise-induced hearing loss,and elucidate its underlying regulatory mechanisms.We established a mouse model of permanent threshold shift hearing loss by exposing the mice to white broadband noise at a sound pressure level of 120 d B for 4 hours.We found that tranylcypromine treatment led to the upregulation of Sestrin2(SESN2)and activation of the autophagy markers light chain 3B and lysosome-associated membrane glycoprotein 1 in the cochleae of mice treated with tranylcypromine.The noise exposure group treated with tranylcypromine showed significantly lower average auditory brainstem response hearing thresholds at click,4,8,and 16 k Hz frequencies compared with the noise exposure group treated with saline.These findings indicate that tranylcypromine treatment resulted in increased SESN2,light chain 3B,and lysosome-associated membrane glycoprotein 1 expression after noise exposure,leading to a reduction in levels of 4-hydroxynonenal and cleaved caspase-3,thereby reducing noise-induced hair cell loss.Additionally,immunoblot analysis demonstrated that treatment with tranylcypromine upregulated SESN2 expression via the autophagy pathway.Tranylcypromine treatment also reduced the production of NOD-like receptor family pyrin domaincontaining 3(NLRP3)production.In conclusion,our results showed that tranylcypromine treatment ameliorated cochlear inflammation by promoting the expression of SESN2,which induced autophagy,thereby restricting NLRP3-related inflammasome signaling,alleviating cochlear hair cell loss,and protecting hearing function.These findings suggest that inhibiting lysine-specific demethylase 1 is a potential therapeutic strategy for preventing hair cell loss and noise-induced hearing loss.

Prevalence of Noise-Induced Hearing Loss Related to the Mills in the Markets of the Municipality of Parakou in 2021

Introduction: Noise is the second leading cause of hearing loss in adults after presbycusis. The objective of this work was to study hearing loss induced by the noise of mills in the markets of Parakou. Methods: This was a descriptive and analytical cross-sectional study, conducted from February 3 to June 3, 2021 in the markets of Parakou. It concerned millers and sellers located within a 5 meter radius around the mills and among whom pure-tone audiometry was performed to detect a hearing loss. Subjects with no particular medical health history, under 55 years of age and having been working in these markets since more than 12 months, were included. Results: In this study, 103 subjects were selected, including 43 millers and 61 sellers. Their average age was 29 ± 13 years. The sex ratio was 0.49. The average length of service in the profession was 8 years with the extremes of 3 months and 47 years. They were exposed to noise on average 10 hours per day and 6 days a week. The average duration of weekly noise exposure was 23 h 28 min ± 13 h 32 min with the extremes of 5 h 00 min and 52 h 30 min. The average level of noise exposure was 90 dB with the extremes of 72 and 110 dB. 24 subjects reported symptoms related to noise such as headache, tinnitus, and hearing loss, with respective proportions of 22.33%, 20.39% and 06.80%. The prevalence of noise-related hearing loss was 26.21% (n = 27/103). Subjects with a notch at 4000 Hz and normal Average Hearing Loss (AHL) (20.39%) had a seven-time greater risk of developing noise-induced hearing loss (OR = 6.58;95% CI [2.54 - 18.8], p Conclusion: Hearing loss related to the noise of mills affected both millers and sellers near the mills in markets, hence the importance of regulating mills.

Myosin-7A Mutation Screening in Patients with Prelingual Non-Syndromic Hearing Impairment

Objective To screen for mutations in myosin-7A gene(MYO7A) in patients with prelingual nonsyndromic hearing impairment. Methods 31 sporadic patients with congenital hearing impairment and 65 patients from 34 families with prelingual hereditary hearing impairment in China were tested in this study, and 100 hearing normal individuals were used as control. Genomic DNA isolated from whole blood of all subjects was subjected to polymerase chain reaction(PCR) to amplify selected exons of MYO7A gene. The PCR products were subsequently screened using single strand conformational polymorphism analysis(SSCP) and direct sequencing when the fragments showed an abnormal electrophoretic pattern. Results GgA transition at position 617 in exon 7, which would produce an A206G amino acid substitution, was detected in two patients but in none of the unaffected members in the families. This heterozygous missense mutation happened within a highly conserved heptapeptide sequence of MYO7A protein, and is closely relevant to preligual nonsyndromic deafness. Conclusions The A206G substitution is possibly a new mutation to cause preligual nonsyndromic hearing impairment. Our results provide evidence that exon 7 of MYO7A is a mutational hotspot in genetic hearing impairment.

Does Hearing Impairment Have an Impact on the Children’s Education in Casamance, South of Senegal?

Goal: To determine the impact of deafness on the schooling of children in Casamance and the factors that characterize these repercussions. Patients and Methods: This was a retrospective, cross-sectional and multicenter study carried out in the ENT departments of the peace and regional hospitals of Ziguinchor over a period of 7 years from January 1, 2012 to December 31, 2019. It included hearing impaired children aged 1 to 18. Results: 178 hearing impaired children were collected during the study period. One hundred and forty-seven children were in school (82, 58%), the majority (85.03%) attending formal schools. Fifty-seven children had a speech disorder (32.02%). The average age of screening for deafness was 9 years. Deafness was mild in 53 patients. Thirteen patients had severe deafness. Two patients presented with cophosis. Conclusion: Our study shows that deafness does indeed have an impact on a child’s education in Casamance, but this impact is hardly taken into account.

Early detection of noise-induced hearing loss

BACKGROUND Noise-induced hearing loss(NIHL)is the second most common acquired hearing loss following presbycusis.Exposure to recreational noise and minimal use of hearing protection increase the prevalence of NIHL in young females.NIHL is irreversible.Identifying minor hearing pathologies before they progress to hearing problems that affect daily life is crucial.AIM To compare the advantages and disadvantages of extended high frequency(EHF)and otoacoustic emission and determine an indicator of hearing pathologies at the early sub-clinical stage.METHODS This cross-sectional study was implemented in West China Hospital of Sichuan University from May to September 2019.A total of 86 participants,aged 18-22 years,were recruited to establish normative thresholds for EHF.Another 159 adults,aged 18-25 years with normal hearing(0.25-8 kHz≤25 dBHL),were allocated to low noise and noise exposure groups.Distortion otoacoustic emission(DPOAE),transient evoked otoacoustic emissions(TEOAE),and EHF were assessed in the two groups to determine the superior technique for detecting early-stage noise-induced pathologies.The chi-square test was used to assess the noise and low noise exposure groups with respect to extended high-frequency audiometry(EHFA),DPOAE,and TEOAE.P≤0.05 was considered statistically significant.RESULTS A total of 86 participants(66 females and 20 males)aged between 18 and 22(average:20.58±1.13)years were recruited to establish normative thresholds for EHF.The normative thresholds for 9,10,11.2,12.5,14,16,18,and 20 kHz were 15,10,20,15,15,20,28,and 0 dBHL,respectively.A total of 201 participants were recruited and examined for eligibility.Among them,159 adults aged between 18 and 25 years were eligible in this study.No statistical difference was detected between the noise exposure and the low noise exposure groups using EHFA,DPOAE,and TEOAE(P>0.05)except in the right ear at 4 kHz using TEOAE(abnormal rate 20.4%vs 5.2%,respectively;P=0.05).CONCLUSION These results showed TEOAE as the earliest indicator of minor pathology compared to DPOAE and EHFA.However,a multicenter controlled study or prospective study is essential to verify these results.

Involvement of NLRP3-inflammasome pathway in noise-induced hearing loss

The inflammasome is a multiprotein oligomer in the cell cytoplasm and is part of the innate immune system.It plays a crucial role in the pathological process of noise-induced hearing loss(NIHL).However,the mechanisms of NLR family pyrin domain containing 3(NLRP3)inflammasome activation in NIHL have not been clearly demonstrated.In this study,miniature pigs were exposed to white noise at 120 dB(A)and auditory brainstem response measurements were used to measure their hearing function.Immunofluorescence staining,confocal laser scanning microscopy,western blot assay,and quantitative reverse transcription-polymerase chain reaction were used to analyze inflammasome-related protein distribution and expression.NLRP3,interleukin-1β,interleukin-18,and cleaved-caspase-1 were highly expressed in the cochlea after 120 dB(A)white noise exposure.Our findings suggest that NLRP3-inflammasomes in the cochlea may be activated after acoustic trauma,which may be an important mechanism of noise-induced hearing loss.

Saturated hydrogen saline protects against noise-induced hearing loss

Objective To study effects of saturated hydrogen saline in preventing noise-induced hearing loss. Methods Fifteen guinea pigs were randomly divided into 3 groups （5 each）, group one was for control, group two was treated with normal saline and group three was treated with saturated hydrogen saline, which was given intraperitoneally at 1 hour before noise exposure at 1 ml/100 g. One hundred rounds of impulse noise （ 157 dB SPL peak） were delivered as noise exposure. Immediately after exposure to impulse noise and on Days 1, 2, 4 and 8 following exposure, auditory brainstem response （ABR） thresholds were measured. Outer hair cell morphological changes and sueeinate dehydrogenase （SDH） activity were examined on Day 8 post-exposure. Results Immediately after noise exposure, ABR thresholds in saturated hydrogen saline treated animals were lower than the non-treated animals （P 〈 0.05 ）. Microscopy showed little SDH staining, cell swelling and irregular cell arrangement in the non-treated or normal saline treated animals. Whereas in the saturated hydrogen saline treated animals, there was deep SDH staining with significantly reduced cell loss and more regular cellular arrangement compared to the other two groups. The surviving cells counts was 45.17 ±12.15 for non-treated animals, 44.50 ±10.02 for normal saline treated animals and,116.50±2.38 for animals treated with saturated hydrogen saline. While the count was similar between non-treated and normal saline treated animals, it was significantly higher in saturated sions Intraperitoneal injection of saturated hydrogen saline damage. hydrogen saline treated animals （P 〈 0.05）. Concluappears to protect the cochlea against noise-induced damage.

NRN1 and CAT Gene Polymorphisms, Complex Noise, and Lifestyles interactively Affect the Risk of Noise-induced Hearing Loss

Objective The effects of interactions between genetic and environmental factors on the noise-induced hearing loss(NIHL)are still unclear.This study aimed to assess interactions among gene polymorphisms,noise metrics,and lifestyles on the risk of NIHL.Methods A case-control study was conducted using 307 patients with NIHL and 307 matched healthy individuals from five manufacturing industries.General demographic data,lifestyle details,and noise exposure levels were recorded.The Kompetitive allele-specific polymerase chain reaction(KASP)was used to analyze the genotypes of 18 SNPs.Results GMDR model demonstrated a relevant interaction between NRN1 rs3805789 and CAT rs7943316(P=0.0107).Subjects with T allele of rs3805789 or T allele of rs7943316 had higher risks of NIHL than those with the SNP pair of rs3805789-CC and rs7943316-AA(P<0.05).There was an interaction among rs3805789,rs7943316,and kurtosis(P=0.0010).Subjects exposed to complex noise and carrying both rs3805789-CT and rs7943316-TT or rs3805789-CT/TT and rs7943316-AA had higher risks of NIHL than those exposed to steady noise and carrying both rs3805789-CC and rs7943316-AA(P<0.05).The best six-locus model involving NRN1 rs3805789,CAT rs7943316,smoking,video volume,physical exercise,and working pressure for the risk of NIHL was found to be the interaction(P=0.0010).An interaction was also found among smoking,video volume,physical exercise,working pressure,and kurtosis(P=0.0107).Conclusion Concurrence of NRN1 and CAT constitutes a genetic risk factor for NIHL.Complex noise exposure significantly increases the risk of NIHL in subjects with a high genetic risk score.Interactions between genes and lifestyles as well as noise metrics and lifestyles affect the risk of NIHL.

An update on hearing impairment in patients with rheumatoid arthritis

Rheumatoid arthritis(RA) is a systemic, autoimmune disease that present with intra-articular and extra-articular manifestations. Auditory system may be involved during the course of RA disease due to numbers of pathologies. The link between hearing impairment and RA has been discussed in the previous literature. In this study we provide an update on the clinical aspect of hearing impairment in RA. We suggest to test hearing in all newly diagnosed RA patients at diagnosis as well as regularly during the course of disease.

Peri-Operative Hearing Impairment

Peri-operative hearing impairment is a poorly reported morbidity following any type of anaesthesia. We report a case where the patient developed temporary hearing impairment after a gynaecological surgery. This recovered in a couple of week time. The causes of such hearing impairment in various types of anaesthesia are discussed.

Disability and Quality of Life among Elderly Persons with Self-Reported Hearing Impairment: Report from the Ibadan Study of Aging

Background: Despite a high prevalence of hearing impairment (HI) among the elderly, the effect on their quality of life (QOL) has not been well studied in this environment. Aim: To determine the prevalence of disability and profile of QOL among elderly persons (aged ≥65 years) with HI. Design of Study: Cross-sectional. Setting: Eight contiguousYoruba-speaking states in Nigeria. Methods: Face-to-face interviews of respondents selected using a multi-stage, stratified area probability sampling of households;HI was based on self report and observer confirmation and the QOL was measured with the World Health Organization brief version (WHOQOL-Bref). Results: The prevalence of disability in Activities of Daily Living (ADL) was 35.4% while it was 10.1% in Instrumental ADL. Prevalence increased significantly with increasing age (P = 0.05). Disability in ADL (P = 0.01), poor family interaction (P = 0.01), poor community involvement (P = 0.01) cognitive impairment (P = 0.05) and poor report of overall health (P = 0.05) were significantly more common among the elderly with HI than those without. No significant differences were found in regard to current depression or the likelihood of experiencing verbal, physical or emotional abuses. Logistic regression analyses adjusting for age, sex, chronic medical conditions and disability confirmed the salient effect of HI on the decrement in the physical domains (P = 0.05). Conclusion: HI is associated with high prevalence of disability and has adverse effect on the quality of life. This observation strengthens the need for hearing rehabilitation in the policy formulation on the care of the elderly in resource-poor settings.

Andrographolide Attenuates Noise-Induced Hearing Loss by Ameliorating Cochlear Inflammation

Objective:This study aimed to explore andrographolide's mechanism of action and its protective effect on noise-induced hearing loss(NIHL).Materials and Methods:A mice animal model for NIHL was established through exposure to broadband noise at 120 d B sound pressure level for 4 h.Transcriptomics analysis and pharmacodynamic experiments were carried out.Results:Andrographolide enters the inner ear and effectively prevents hearing damage following noise exposure in the mice model for permanent hearing loss.Moreover,treatment with andrographolide inhibited the excessive activation of inflammatory factors in the cochleae of noise-exposed mice.Conclusion:Andrographolide might be a promising candidate for auditory protective drug investigation.

Medical Therapy of Hearing Impairment and Tinnitus with Chinese Medicine:An Overview

The current review gives a comprehensive overview of the recent development in Chinese medicine(CM)for treating several kinds of acquired nerve deafness and tinnitus,as well as links the traditional principle to well-established pharmacological mechanisms for future research.To date,about 24 herbal species and 40 related ingredients used in CM to treat hearing loss and tinnitus are reported for the treatment of endocochlear potential,endolymph growth,lowering toxic and provocative substance aggregation,inhibiting sensory cell death,and retaining sensory transfer.However,there are a few herbal species that can be used for medicinal purposes.Nevertheless,clinical studies have been hampered by a limited population sample,a deficiency of a suitable control research group,or contradictory results.Enhanced cochlear blood flow,antiinflammatory antioxidant,neuroprotective effects,and anti-apoptotic,as well as multi-target approach on different auditory sections of the inner ear,are all possible benefits of CM medications.There are numerous unknown natural products for aural ailment and tinnitus identified in CM that are expected to be examined in the future utilizing various aural ailment models and processes.

Identification of Two Disease-causing Genes TJP2 and GJB2 in a Chinese Family with Unconditional Autosomal Dominant Nonsyndromic Hereditary Hearing Impairment

Background： There are more than 300 genetic loci that have been found to be related to hereditary hearing impairment （HHI）, including 92 causative genes for nonsyndromic hearing loss, among which 34 genes are related to autosomal dominant nonsyndromic HHI （ADNSHH 1）. Traditional linkage analysis and candidate gene sequencing are not effective at detecting the ADNSHHI, especially for the unconditional families that may have more than one pathogenic cause. This study identified two disease-causing genes TJP2 and GJB2 in a Chinese family with unconditional ADNSHHI. Methods： To decipher the genetic code of a Chinese family （family 686） with ADNSHHI, different gene screening techniques have been performed, including linkage analysis, candidate genes screening, high-throughput sequencing and Sanger sequencing. These techniques were done on samples obtained from this family over a period of 10 years. Results： We identified a pathogenic missense mutation, c. 2081G〉A （p.G694E）, in TJP2, a gene that plays a crucial role in apoptosis and age-related hearing loss （ARHL）. The mutation was co-segregated in this pedigree in all, but not in the two patients who presented with different phenotypes from the other affected family members. In one of the two patients, we confirmed that the compound heterozygosity for p.Y136^＊ and p.G45E in the GJB2 gene may account for the phenotype shown in this patient. Conclusions： We identified the co-occurrence of two genetic causes in family 686. The possible disease-causing missense mutation of TJP2 in family 686 presents an opportunity for further investigation into ARHL. It is necessary to combine various genes screening methods, especially for some unconventional cases.

Single nucleotide polymorphisms and haplotypes analysis of DFNB1 locus in Chinese sporadic hearing impairment population

Background The DFNB1 locus, which contains the gap junction beta-2 （GJB2） and gap junction beta-6 （GJB6） genes, plays a key role in the nonsyndromic and sporadic hearing impairment. Mutations of DFNB1 result in autosomaJ recessive nonsyndromic hearing impairment （ARNSHI）. Previous researches have identified mutations in GJB2 and GJB6, but single nucleotide polymorphisms （SNPs） of DFNB1 locus have not been studied. So we chose five SNPs to evaluate whether there is difference between deafness people and normal-hearing people in Han Chinese. Methods Five SNPs in the DFNB1 region were examined using a case-control association study between cases with sporadic hearing impairment and controls with normal hearing. The HWEsoft and SHEsis softwares were used to analyze the results. Results Single-locus association analysis showed a positive association for three SNPs： rs9315400, rs2274084 and 235delC. When we compared the distributions of the haplotypes, we also found significant differences between cases and controls in the haplotype combination of rs2274084 and rs2274083 （Х^2=12.978, df=3, global P=0.004719）. Conclusions The haplotypes composed of rs2274084 and rs2274083 suggested that C-C may be a risk haplotype for the sporadic hearing impairment while T-T may be protective against hearing impairment. From that point of view, we can conclude that the SNPs of DFNB1 locus also plays an important role in sporadic hearing impairment cases.

Etiology of newborn hearing impairment in Guangdong province: 10-year experience with screening, diagnosis, and follow-up

Background Hearing impairment is one of the most common birth defects in children.Universal newborn hearing screenings have been performed for 19 years in Guangdong province,China.A screening/diagnosis/intervention system has gradually been put in place.Over the past 10 years,a relatively complete data management system had been established.In the present study,an etiological analysis of newborn cases that failed the initial and follow-up screenings was performed.Methods The nature and degree of hearing impairment in newborns were confirmed by a set of procedures performed at the time of initial hearing screening,rescreening and final hearing diagnosis.Then,multiple examinations were performed to explore the associated etiology.Results Over a period of 10 years,720 children were diagnosed with newborn hearing loss.Among these children,445 (61.81%) children had a clearly identified cause,which included genetic factor(s) (30.56%),secretory otitis media (13.30%),maternal rubella virus infection during pregnancy (5.83%),inner ear malformations (4.86%),maternal human cytomegalovirus infection during pregnancy (2.92%),malformation of the middle ear ossicular chain (2.50%) and auditory neuropathy (1.81%).In addition,275 cases of sensorineural hearing loss of unknown etiology accounted for 38.19% of the children surveyed.Conclusions Long-term follow-up is needed to detect delayed hearing impairment and auditory development in children.The need for long-term follow-up should be taken into account when designing an intervention strategy.Furthermore,the use of the deafness gene chip should further elucidate the etiology of neonatal hearing impairment.

Phenotype and genotype analysis of a Chinese family with prelingual X-linked hereditary hearing impairment

Background X-linked hearing impairment is clinically and genetically a heterogeneous disease. Although many disorders manifest with hearing loss, a limited number of sex-linked loci and only one gene （POU3F4） have been shown to be implicated in X-linked non-syndromic hearing impairment. In the present study, we have performed a clinical and genetic analysis of a Chinese family with X-linked non-syndromic hearing loss, with emphasis on audiological findings and genomic mapping. Methods The clinical features of Family JX01 were evaluated by physical and audiometric examination in eighteen family members. Mutation screening of POU3F4 was identified by polymerase chain reaction （PCR） amplification and sequencing. Molecular evaluation consisted of X-chromosome wide genotyping by microsatellite makers （STR）, followed by analyzing using MLINK computer program. Results Five affected males demonstrated bilateral, symmetrical sensorineural and profound hearing loss. The hearing impairment started prelingual. The female carriers did not have any complain of hearing loss, however, two of them were tested with milder loss with high frequency. No causative mutations in POU3F4 gene were detected by DNA sequencing. Linkage analysis indicated that the responsible gene was linked to locus DXS1227 （maximum Iod score=2.04 at θ=0）. Conclusions The affected males in Family JX01 have profound prelingual sensorineural hearing impairment. In addition, two female carriers showed mild to moderate hearing losses. However, none of females complained of any hearing loss. Analysis of hereditary deafness in this family mapped most compatibly to the Xq27.2.

Prophylactic effect of Ca^(2+)-deficient artificial perilymph perfusion on noise-induced hearing loss

Objective To investigate the prophylactic effect of low calcium concentration perilymph on noise-induced hearing loss. Methods Forty guinea pigs with normal hearing weighing 250-350 g were assigned to five groups (8 in each group): (1) Ca2+-deficient perilymph perfusion (CDP) for 2 h; (2) white noise (120 dB SPL) exposure (WNE) only for 1 h, (3) combination of calcium-deficient perilymph perfusion and white noise (120 dB SPL) exposure (WNE+CDP); (4) normal artificial perilymph (NAP) perfusion for 2 h; and (5) white noise exposure + normal artificial perilymph perfusion (WNE+NAP) for 2 h. Compound action potentials (CAP) evoked by click was recorded from round window every 15 min. The cochleae from 5 animals in each group were examined with scanning electron microscope. Results The CAP for group 1 experienced a threshold shift (TS) of 15-26 dB, while group 2 yielded a 46-59 dB TS and group 3 a 37-45 dB TS; no threshold shift occurred in group 4. The CAP TS in group 5 was 33-64 dB. The CAP TS of group 3 was less than that of group 2. After one hour of noise exposure, the CAP TS of group 3 were 45.92±2.90 dB and 59.30±3.95dB in group 2. There were significant differences (P<0.05) between groups 3 and 2. The CAP TS of group 3 was less than that of group 5 at the points of 1, 1.5 and 2 h after noise exposure. There was a significant difference between groups 3 and 5 (P<0.01). Stereocilia of 89 OHC3 were in disarray in five cochleae after noise exposure in group 2. The cuticular plates of 8 OHC2,3 sank and the stereocilia became fused in only one animal cochlea after noise exposure in group 3 combined with low calcium perilymph perfusion. Conclusions Low calcium concentration appears to participate in preventing noise-induced hearing loss and the rising of calcium concentrations in inner hair cells after noise exposure, which may have been due to the opening of calcium channels in inner hair cells during noise exposure. The mechanism of the prophylactic effect might be caused by a lower calcium concentration in inner hair cells in the cochlea attenuating the influence of noise exposure on hearing loss; calcium deficient perilymph perfusion prevented calcium accumulation in inner hair cells of the cochlea. The motility of the OHCs might be partially inhibited by low calcium concentration that reduced noise-induced hearing loss in turn.