EFFECTS OF MODERATE NOISE EXPOSURE ON HEARING FUNCTION IN C57BL/6J MICE

Objective To study characteristics of hearing loss after exposure to moderate noise exposure in C57BL/6J mice. Methods Male C57BL/6J mice with normal hearing at age of 5-6 weeks were chosen for this study. The mice were randomly sclccted to be studied immediately after exposure （Group P0）, or 1 day （Group P1）, 3 days （Group P3）, 7 day （Group P7） or 14 days （P14） after exposure. Their before exposure condition served as the normal control. All mice were exposed to a broad-band white noise at 100 dB SPL for 2 hours, ABR thresholds were used to estimate hearing status at each time point. Results ABR threshold elevation was seen at every tested frequency at P0 （P〈0.01）. Elevation at high-frequencies （16 kHz and 32 kHz） was greater than at lower frequencies （4 kHz and 8 kHz, P〈0.05）. From P1 to P14, ABR thresholds continuously improved, and there was no significant difference between P14 and before exposure （P〉0.05）. Conclusion There is a frequency specific re- sponse to 100 dB SPL broad-band white noise in C57BL/6J mice, with the high-frequency being more susceptible. Hearing loss induced by moderate noise exposure appears reversible in C57BL/6J mice.

Noise exposure induced cochlear hair cell death pathways in guinea pig

Objective To understand the mechanism of noise exposure induced outer hair cells(OHCs) death pathways. Methods Thirty two guinea pigs were used in this study. The animals were either exposed for 4 h/day to broadband noise at 122 dB SPL (A-weighted) for 2 consecutive days or perfused with MNNG. After auditory test, the cochleae of animals were dissected. Propidium iodide (PI), a DNA intercalating fluorescent probe, was used to trace morphological changes in OHC nuclei. F-actin staining was used to determine missing OHCs. Caspase-3 was detected in living organ of Corti whole mounts using the fluorescent probe. The single strand DNA (ssDNA) in apoptotic OHCs in guinea pigs and apoptosis inducing factor (AIF) in hair cells in guinea pigs were examined by immunohistology method. Whole mounts of organ of Corti were prepared. Morphological and fluorescent changes were examined under a confocal microscope. Results (1) Both apoptotic and necrotic hair cells appeared following noise exposure. (2) Noise exposure induced single strand DNA in apoptotic OHCs but not in the normal OHCs. (3) Either after noise exposure or after MNNG perfusion, apoptotic OHCs were featured by nuclear condensation or fragmentation with caspase-3 activation, whereas necrotic OHCs were characterized by nuclear swelling without caspase-3 activation. (4) In normal organ of Corti, AIF was located in the mitochondria areas. After noise exposure, AIF was translocated from mitochondria in apoptotic and necrotic OHCs. Conclusion These findings indicate that noise exposure damages DNA in the OHC, which triggers action of Caspase-3. Subsequently, AIF is translocated to the nucleus, leading to DNA damage and OHCs death.

Influence of Occupational Noise Exposure on Cognitive Ability of Grinders

Purpose: To investigate whether long-term noise exposure affects the cognitive ability of grinders. Methods: Cumulative noise exposure (CNE) and LAeq.8h determination were used to characterize the level of individual noise exposure;the Montreal Cognitive Assessment (MoCA) test (Beijing version) was used to evaluate cognitive function. Results: We compared the basic situation of workers in different groups and individual noise exposure intensity of grinders was monitored. Multiple linear-regression analysis was made and score of MoCA in different group was finally drawn. Conclusion: CNE and total score of MoCA have the relationship of negative correlation (r = -0.303, p < 0.05) which means long-term occupational noise exposure can affect the cognitive ability of grinders.

The effect of noise exposure on sleep quality of urban residents:A comparative study in Shanghai,China

Noise exposure is becoming extremely common in urban area,but its specific impact on sleep remains controversial.Considering the limitations of previous researches,a field study which can conduct both horizontal and longitudinal analysis was designed.Urban participants were tested during two weeks in their homes,and the noise level of bedroom was artificially regulated by changing the status of window and door.During the 1050 test nights in 75 households,noise exposure was reflected from both instrument monitoring at night and perception questionnaire in the morning,and sleep quality was accessed from actigraphy and questionnaire.The analysis results showed that,92.3%of the bedroom acoustic environment did not meet the minimum requirements of Chinese standards,and 87.9%of subjects had ever experienced harmful noise during the test period.Furthermore,sleep quality was affected by noise exposure from the perspective of both physiological and psychological;the duration of rapid eye movement(REM)sleep was significantly(p<0.05)shortened with the increase of sound intensity,the duration of deep sleep shortened and subjective sleep quality worsened significantly(p<0.05)with the increase of acoustic sensation vote.In addition,females were more sensitive to noise exposure and their subjective sleep quality was more likely to be influenced by emotions.This study has important implications for acoustic environment design of bedrooms in cities,and suggested more attention should be paid to the anxiety caused by noise exposure.

Associations of blood pressure and arterial compliance with occupational noise exposure in female workers of textile mill

Background There are few studies on the arterial compliance of noise exposure. The purpose of this study was to understand the relationship between hearing loss, blood pressure and arterial compliance of female workers who exposed to occupational noise in a textile mill. Methods The noise levels in the workplace were measured with a HS6288 sound level meter. Cumulated noise exposure （CNE） was calculated according to the noise intensity and the exposure period. Hearing ability and arterial compliance were measured in 618 noise exposed workers. The database was set up with EpiData and the statistical analysis was performed with SAS software 9.1.3. Results The noise levels were 80.1dB（A） to 113.5dB（A）, of which the levels at 92.5% of the noise monitoring sites were over the national standard. The incidence of high frequency hearing loss （HFHL） was 24.43% and language frequency hearing impairment （LFHI） was 0.81%. The incidence of hypertension was 7.93%. Both systolic blood pressure （SBP） and diastolic blood pressure （DBP） in the high frequency hearing loss group were significantly higher than those in the normal hearing group （P〈0.05）, while C1 （large artery compliance） and C2 （small artery compliance） were significantly lower （P〈0.05）. The high frequency hearing threshold （HFHT） of the hypertension group was significantly higher than in the normal blood pressure group （P〈0.05）, while C1 and C2 were significantly lower （P〈0.05）.C1 and C2 had a negative correlation with HFHT, SBP, DBP, mean of arterial pressure （MAP）, pulse pressure （PP） and pulse rate （PR） （P〈0.05）. The multiple regression analyses showed that blood pressure and PR were the main influencing factors on C1 and C2. LFHT was an influence on C2 and HFHT on C1. Conclusions Textile mill noise pollution is very serious and has an obvious influence on worker＇s auditory function. The female workers with low artery compliance or with high blood pressure might be suffering from hearing loss; those with noise induced hearing loss might be suffering from hypertension if she is constantly exposed to loud industrial noise.

PTEN inhibitor bisperoxovanadium protects against noise-induced hearing loss

Studies have shown that phosphatase and tensin homolog deleted on chromosome ten(PTEN)participates in the regulation of cochlear hair cell survival.Bisperoxovanadium protects against neurodegeneration by inhibiting PTEN expression.However,whether bisperoxovanadium can protect against noise-induced hearing loss and the underlying mechanism remains unclear.In this study,we established a mouse model of noise-induced hearing loss by exposure to 105 dB sound for 2 hours.We found that PTEN expression was increased in the organ of Corti,including outer hair cells,inner hair cells,and lateral wall tissues.Intraperitoneal administration of bisperoxovanadium decreased the auditory threshold and the loss of cochlear hair cells and inner hair cell ribbons.In addition,noise exposure decreased p-PI3K and p-Akt levels.Bisperoxovanadium preconditioning or PTEN knockdown upregulated the activity of PI3K-Akt.Bisperoxovanadium also prevented H_(2)O_(2)-induced hair cell death by reducing mitochondrial reactive oxygen species generation in cochlear explants.These findings suggest that bisperoxovanadium reduces noise-induced hearing injury and reduces cochlear hair cell loss.

Machine learning noise exposure detection of rail transit drivers using heart rate variability

Previous studies have found that drivers’physiological conditions can deteriorate under noise conditions,which poses a potential hazard when driving.As a result,it is crucial to identify the status of drivers when exposed to different noises.However,such explo-rations are rarely discussed with short-term physiological indicators,especially for rail transit drivers.In this study,an experiment involving 42 railway transit drivers was conducted with a driving simulator to assess the impact of noise on drivers’physiological responses.Considering the individuals’heterogeneity,this study introduced drivers’noise annoyance to measure their self-noise-adaption.The variances of drivers’heart rate variability(HRV)along with different noise adaptions are explored when exposed to different noise conditions.Several machine learning approaches(support vector machine,K-nearest neighbour and random forest)were then used to classify their physiological status under different noise conditions according to the HRV and drivers’self-noise adaptions.Results indicate that the volume of traffic noise negatively affects drivers’performance in their routines.Drivers with different noise adaptions but exposed to a fixed noise were found with discrepant HRV,demonstrating that noise adaption is highly associated with drivers’physiological status under noises.It is also found that noise adaption inclusion could raise the accuracy of classifications.Overall,the random forests classifier performed the best in identifying the physiological status when exposed to noise conditions for drivers with different noise adaptions.

Acoustic trauma-induced auditory cortex enhancement and tinnitus

There is growing evidence suggests that noise-induced cochlear damage may lead to hyperexcitability in the central auditory system(CAS)which may give rise to tinnitus.However,the correlation between the onset of the neurophysiological changes in the CAS and the onset of tinnitus has not been well studied.To investigate this relationship,chronic electrodes were implanted into the auditory cortex(AC) and sound evoked activities were measured from awake rats before and after noise exposure.The auditory brainstem response(ABR) was used to assess the degree of noise-induced hearing loss.Tinnitus was evaluated by measuring gap-induced prepulse inhibition(gap-PPI).Rats were exposed monaurally to a high-intensity narrowband noise centered at 12 kHz at a level of 120 dB SPL for 1 h.After the noise exposure,all the rats developed either permanent(>2 weeks) or temporary(<3 days) hearing loss in the exposed ear(s).The AC amplitudes increased significantly 4 h after the noise exposure.Most of the exposed rats also showed decreased gap-PPI.The post-exposure AC enhancement showed a positive correlation with the amount of hearing loss.The onset of tinnitus-like behavior was happened after the onset of AC enhancement.

PERIPHERAL HEARING LOSS CAUSES HYPEREXCITABILITY OF THE INFERIOR COLLICULUS

Growing evidence has been found to suggest that early development of the central auditory system is dependent on acoustic stimuli. Peripheral damage caused by noise exposure and ototoxic drugs can induce functional and anatomical changes along the auditory pathways. The inferior colliculus (IC) is a unique structure in the auditory system located between the primary auditory nuclei of the brainstem and the thala-mus. Damage to the IC inhibitory circuitry may affect central auditory processing and sound perception. Here, we review some of the striking electrophysiological changes in the IC that occur after noise exposure and ototoxic drug treatment. A common occurrence that emerges in the IC after peripheral damage is hyper-excitability of sound-evoked response. The hyperexcitability of the IC is likely related with reduced inhibi-tory response that requires normal peripheral inputs. Early age hearing loss can result in a long lasting in-creased susceptibility to audiogenic seizure which is related to hyperactivity in the IC evoked by loud sounds. Our studies suggest that hearing loss can cause increased IC neuron responsiveness which may be related to tinnitus, hyperacusis, and audiogenic seizure.

ANIMAL BEHAVIORAL MODELS OF TINNITUS

The pathophysiology of tinnitus is poorly understood and treatments are often unsuccessful. A number of animal models have been developed in order to gain a better understanding of tinnitus. A great deal has been learned from these models re- garding the electrophysiological and neuroanatomical correlates of tinnitus following exposure to noise or ototoxic drugs. Re- liable behavioral data is important for determining whether such electrophysiological or neuroanatomical changes are indeed related to tinnitus. Of the many documented tinnitus animal behavioral paradigms, the acoustic startle reflex had been pro- posed as a simple method to identify the presence or absence of tinnitus. Several behavioral models based on conditioned re- sponse suppression paradigms have also been developed. In addition to determining the presence or absence of tinnitus, some of the behavioral paradigms have provided signs of the onset, frequency, and intensity of tinnitus in animals. Although none of these behavioral models have been proved to be a perfect model, these studies provide useful information on understanding the neural mechanisms underlying tinnitus.

Noise-induced nitrotyrosine increase and outer hair cell death in guinea pig cochlea

Background Modern research has provided new insights into the biological mechanisms of noise-induced hearing loss, and a number of studies showed the appearance of increased reactive oxygen species （ROS） and reactive nitrogen species （RNS） during and after noise exposure. This study was designed to investigate the noise exposure induced nitrotyrosine change and the mechanism of outer hair cells death in guinea pig cochlea. Method Thirty guinea pigs were used in this study. The experimental animals were either exposed for 4 hours per day to broadband noise at 122 dB SPL （A-weighted） for 2 consecutive days or perfused cochleae with 5 mg/ml of the SIN1 solutions, an exogenous NO and superoxide donor, for 30 minutes. Then the cochleae of the animals were dissected. Propidium iodide （PI）, a DNA intercalating fluorescent probe, was used to trace morphological changes in OHC nuclei. The distribution of nitrotyrosine （NT） in the organ of Corti and the cochlear lateral wall tissue from the guinea pigs were examined using fluorescence immunohistochemistry method. Whole mounts of organ of Corti were prepared. Morphological and fluorescent changes were examined under a confocal microscope. Results Either after noise exposure or after SIN1 perfusion, outer hair cells （OHCs） death with characteristics of both apoptotic and necrotic degradation appeared. Nitrotyrosine immunolabeling could be observed in the OHCs from the control animals. After noise exposure, NT immunostaining became much greater than the control animals in OHCs. The apoptotic OHC has significant increase of nitrotyrosine in and around the nucleus following noise exposure. In the normal later wall of cochleae, relatively weak nitrotyrosine immunolabeling could be observed. After noise exposure, nitrotyrosine immunoactivity became stronger in stria vascularis. Conclusion Noise exposure induced increase of nitrotyrosine production is associated with OHCs death suggesting reactive nitrogen species participation in the cochlear pathophysiology of noise-induced hearing loss.

Effect of intensity and duration of anthropic noises on European mink locomotor activity and fecal cortisol metabolite levels

Human activities involving noise emission can affect wild animals.European mink was exposed to road noise and human voice playbacks to analyze how sound intensity level and duration of both noises altered the time that individuals were active and if their fecal cortisol metabolite(FCM)levels varied.A Hierarchical Analysis Cluster was performed to establish 2 mink groups with respect to both noise source type:short duration/low intensity(SL)and long duration/high intensity(LH).We performed general linear mixed models to evaluate the variation in locomotor activity duration(s)and FCM(nanogram per gram)levels,respectively.The results showed both road noise and human voices decreased locomotor activity duration in SL more sharply compared with LH,and human voices were the triggers that induced the most pronounced response to both exposure conditions.FCM(ng/g)levels increased in SL compared with LH during road noise while the opposite happened during human voices.Differences based on sex and age of individuals were observed.In conclusion,noise characteristics given by the sound type determined the variations in locomotor activity duration while noise exposure level determined the variations in FCM(ng/g)levels.Attention should be paid to noisy activities(e.g.,recreational activities for visitors in protected natural areas)and loud groups of people to conserve wildlife,especially noise sensitive species.

Noise levels inside the coaches of Greater Cairo tunnel metro, line 3 tunnel

This paper investigates the noise inside a metro coach running through the most recent tunnel of Cairo.The study focuses on the effects of alignment profiles on the A-weighted noise level.Although the latest line has not been studied yet,noise levels inside the old lines attracted the attention of researchers due to their importance as the first mass transit system in Africa.Given that windows are usually kept open,measurements were conducted inside the empty cabin at the end of the train with open windows according to ISO 3381:2005.Results showed that noise emissions inside the running coaches are high and do not follow either international or general national legislation,which presents health hazards for drivers and commuters.Speech intelligibility is required for train radio units and driver consoles for voice communications,which provides a safe working environment for the train crew.The present study reveals that tight curves mainly contribute to high noise.The noise levels are further raised by the reflective surface of the tunnel with a circular cross-section and the unballasted track.Moreover,the noise level is affected by the location of the coach and window conditions(open/close)to some extent.