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Background: The aim of this study was to assess sound exposure and the risk of noise-induced hearing loss (NIHL) in orchestral musicians., Materials and Methods: Questionnaire inquiries and sound pressure level measurements were carried out in 63 musicians. Based on these data the risk assessment of the NIHL was performed according to ISO 1999:1990 (PN-ISO 1999:1990)., Results: The classical orchestral musicians are usually exposed to sound at equivalent continuous A-weighted sound pressure levels of 81-90 dB (10-90th percentile), for 20-48 h (10-90th percentile) per week. Occupational exposures to such sound levels over 40 years of employment cause the risk of hearing impairment (expressed as mean hearing threshold level for 2, 3 and 4 kHz equal or greater than 25 dB) in the range of 13-33% and 9-33% in females and males, respectively. The highest risk is related to playing clarinet (up to 33%), tube (up to 34%), trumpet (up to 37%), trombone (up to 40%), percussion section (up to 41%) and horn (up to 47%). About 46% of respondents noticed hearing impairment. Nearly every fifth musician complained of tinnitus while almost half (48%) of them--of hyperacusis. However, only 14% of musicians declared present or past usage of hearing protective devices (HPDs) while over twice of them (30%) intended to use HPDs in the future.

Background: Noise prevailing in the non-occupational environment, such as that experienced in disco or rock concerts may be dangerous to the condition of the human hearing organ. The existing methods for assessing the risk of hearing loss (e.g., specified in ISO 1999:1990) fails to consider the contribution of non-occupational noise to the overall noise exposure. The fact that there is no generally accepted method for assessing the contribution of individual exposures to non-occupational noise to be used in epidemiological studies is one of the reasons that the effect of the quoted ISO procedure is limited. The aim of this study was to develop a method enabling quantitative assessment of the individual level of non-occupational noise exposure and estimation of the exposure uncertainty in large groups of people., Material and Methods: Based on the available literature data and our own results, we established a database on noise levels associated with typical circumstances prevailing in the general environment. A questionnaire was developed to enable collection of data essential for defining individual exposures to non-occupational noise. Using the questionnaire data, a procedure for assessing the level of non-occupational noise exposure was developed and its reliability was determined by assessing the repeatability of the results of two determinations performed every three weeks and comparing the calculated levels of the noise exposures with the true levels., Results: The values of individual non-occupational noise exposure, referred to 8h (LEX, 8h) in the study group of people, using the proposed methods ranged between 69 dB and 80 dB. This method allows to assess individual non-occupational exposures to noise at 1-2 dB error relative to the measured levels. The uncertainty of the method is within 4 dB., Conclusions: The proposed method enables a reliable assessment of non-occupational exposure to non-occupational noise and may be successfully applied in epidemiological studies.

Objectives: Individual susceptibility to noise-induced hearing loss (NIHL) depends on the interaction between intrinsic and environmental factors. To proceed with the study on NIHL susceptibility genes an appropriate selection of workers susceptible and resistant to noise is crucial. The aim of the study was to compare four different methods of subject classification by the susceptibility to NIHL in a group of 949 workers of an electric power plant exposed to steady-state noise at the workplace., Materials and Methods: One method based the classification of the workers on the international reference standard ISO 1999:1990; from the entire group of workers, 10% of the subjects with the worst hearing thresholds (HT) in the model were categorized as susceptible to NIHL, whereas 10% of the subjects with the best HT were categorized as resistant to noise. According to three other methods, the entire group of workers was first divided into subgroups by age, duration of employment and the level of noise, and then 10% of the subjects at each HT extreme were selected., Results: The first classification allowed to achieve an excellent separation between HT of the susceptible and resistant subgroups. The susceptible subgroup was significantly younger than the resistant one, showed a shorter duration of employment and a lower level of noise exposure, which is in line with the definition of increased vulnerability to NIHL. The three other methods produced poorer separation of HT with smaller or no gap between HT values in subgroups., Conclusions: The selection of subjects from the entire worker population of a given industry based on the ISO 1999:1990 standard can be regarded as the most reliable method of classification of noise-susceptible and noise-resistant workers to be used in the future genetic studies on NIHL susceptibility genes.

Background: Noise produced by jet engines may be harmful to aircraft servicing personnel because of high levels of acoustic pressure. The aim of the study was to assess the acoustic environment of persons exposed to jet engine noise and its effect on hearing., Materials and Methods: Noise measurements were performed on three jet engines. During the target practice, the following parameters were measured: equivalent noise, pressure level A, maximum sound pressure level A, and peak sound pressure level C. The spectro-analysis covering the range from 0.1 to 20 kHz was conducted. Hearing was assessed in 50 noise-exposed men, aged 24-51 years (mean age, 35.5 years), using PTA, tympanometry and DPOAE. The control group consisted of 40 non-exposed persons with good hearing condition., Results: Maximum levels of acoustic pressure exceeded Polish standards. Comparison between two groups showed that PTA was higher in the exposed persons by 6.3-6.8 dB on average and DPOAE was reduced in the group exposed to jet engine noise more than it could have been expected., Conclusions: Even during a single test, aircraft technical personnel was exposed to (audible) noise that significantly exceeded admissible values. The reduction in DPOAE values in persons exposed to noise of jet engines was incommensurably higher than changes in PTA.

Objectives: Firearm is a common source of impulse noise that may potentially damage hearing organ. It has been suggested that otoacoustic emissions, particularly transient-evoked otoacoustic emissions (TEOAE), might be more sensitive than pure-tone audiometry (PTA) in the assessment of changes to cochlea caused by noise. The aim of this study was to: (i) evaluate exposure to impulse noise from small-caliber weapons, (ii) compare the post-exposure changes in hearing measured by PTA and TEOAE and correlate them with noise parameters., Materials and Methods: The study included 18 male hunters (group I) and 28 candidate policemen (group II) exposed to impulse noise from small firearms during target practices. Group I was unprotected during shooting, whereas group II used commonly available hearing protectors. PTA and TEOAE were performed before and 2-10 min after shooting. Exposure to impulse noise was evaluated by in situ measurements., Results: Groups I and II were exposed to 3-4 and 4-144 impulses of noise at mean C-weighted peak sound pressure levels of 154 dB and 156 dB, respectively. No post-exposure audiometric threshold shift was observed in group I. Significant reductions of TEOAE levels were found both for the whole response (-2.2 dB SPL) and for 1/2 -octave band responses in the frequency range of 1000-4000 Hz (from -1.6 to -3.0 dB SPL). These changes were not correlated with C-weighted peak sound pressure levels or equivalent-continuous A-weighted sound pressure level. Significant correlation was found for peak sound pressure and maximum sound pressure levels in 1/3-octave bands in the frequency range corresponding with the main part of the acoustic energy of impulses (correlation coefficients r from -0.58 to -0.77, p < 0.05). In group II neither PTA nor TEOAE showed significant hearing impairment after shooting., Conclusions: The results show that even short-term exposure to impulse noise from small-calibre firearms might cause temporary hearing impairment measured by TEOAE. Therefore, the use of earmuffs is strongly recommended, because most of them seem to effectively attenuate impulse noise from small-calibre firearms.

Ototoxicity of styrene and the synergistic action of styrene and noise have been shown in rats. The respective data in humans are scarce and equivocal. This study evaluated the effects of occupational exposure to styrene and combined exposures to styrene and noise on hearing. The study group, comprised of 290-yacht yard and plastic factory workers, was exposed to a mixture of organic solvents, having styrene as its main compound. The reference group, totaling 223 subjects, included (1) white-collar workers, exposed neither to solvents nor noise and (2) metal factory workers, exposed exclusively to noise. All subjects were assessed by means of a detailed questionnaire and underwent otorhinolaryngological and audiometric examinations. Multiple logistic regression analysis revealed almost a 4-fold (or 3.9; 95% CI = 2.4-6.2) increase in the odds of developing hearing loss related to styrene exposure. The factors adjusted for were: age, gender, current occupational exposure to noise, and exposure to noise in the past. In cases of the combined exposures to styrene and noise, the odds ratios were two to three times higher than the respective values for styrene-only and noise-only exposed subjects. The mean hearing thresholds--adjusted for age, gender, and exposure to noise--were significantly higher in the solvent-exposed group than in the unexposed reference group at all frequencies tested. A positive linear relationship existed between an averaged working life exposure to styrene concentration and a hearing threshold at the frequencies of 6 and 8 kHz. This study provides the epidemiological evidence that occupational exposure to styrene is related to an increased risk of hearing loss. Combined exposures to noise and styrene seem to be more ototoxic than exposure to noise alone.

Styrene exerts ototoxic effect in animals, and the combined exposure to this solvent and noise produces a synergistic effect relative to the isolated exposure to noise. However, there is a lack of reliable evidence that chronic occupational exposure to styrene is ototoxic to humans. Neither has been documented its additive effect with noise. The present study was aimed to assess hearing impairment and the risk of hearing loss in workers exposed to both styrene and noise. The study group included 72 male workers occupationally exposed to styrene in the plastics industry. The results were compared with two control groups, matched by age, gender and personal traits: one group composed of 82 male workers employed in a printing house and exposed only to noise at the levels almost twice as high as those observed in the group exposed to styrene and noise, and the other consisted of 65 male workers exposed neither to solvents nor to noise at workplace. In the group exposed to styrene and noise, significantly increased average hearing loss, as compared to both control groups, was found at all frequencies (1-8 kHz). The risk of hearing loss in the group exposed to styrene and noise was seven times higher (RR: 6.6; 3.0-15.9) than in the non-exposed group, and four times higher (RR: 4.0; 1.8-9.1) than in when workers exposed only to noise. However, no relationship could be observed between the amount of styrene exposure and hearing impairment, taking account of the confounding effect of noise and age. The results of the study suggest that the exposure to solvent mixtures with styrene as a basic component may exert additional, to noise, adverse effect on the auditory organ.

In mammals, the damage to the hair cells of the inner ear due to exposure to noise or other ototoxic agents is irreversible. In fish, reptiles and birds, however, the hair cells may regenerate, probably from the supporting cells. This regeneration process in the inner ear is being intensively examined in animals in the hope of curing the sensorineural hearing loss in human subjects in future. The aim of the study was to assess hair cell regeneration in the inner ear of chicks after exposure to industrial noise, depending on the level of exposure. The birds were exposed either to the noise at the level of 110 dB (A), 4 hours a day, for 5 consecutive days, or at the level of 125 dB (A), 8 hours a day, for 5 consecutive days. The results confirm that the regeneration starts immediately during the period of recovery from acoustic trauma, and the supporting cells are the main source for new, developing hair cells. Moreover, we found that the complete damage to hair cells is not necessary to the proliferation of supporting cells and that the intensity of proliferation of these cells depends on the level and time of exposure.

It is very difficult to distinguish between occupational noise-induced hearing loss and other diseases with cochlear hearing loss by the means of conventional audiometric tests. Otoacoustic emission measurement is a relatively new tool for assessing the inner ear function. It gives an opportunity of monitoring the status of the outer hair cells, the elements which are the most sensitive to noise-induced damage. In this study the results of distortion product otoacoustic emission (DPOAE) measurement in subjects with industrial noise-induced hearing loss, presbycusis and hearing impairment caused by gentamycin, are presented. In all these cases pure-tone audiometry revealed similar shape of the audiograms with cochlear hearing loss mainly at high frequencies. In the cases of industrial noise-induced hearing loss, DPOAE measurements demonstrated a very typical shape of DP-gram with the decrease (notch) in otoacoustic primarily at the frequencies of 3-4 kHz. Such a notch in DP-grams was not observed in the cochlear hearing loss caused by factors other than noise. The data indicate that otoacoustic emissions may be useful in the differential diagnosis of occupational noise-induced hearing loss.

The use of impedance audiometry for determining hearing threshold and locating hearing impairments was investigated in 112 people exposed to occupational noise. Tympanometry and the stapedius reflex threshold measurements (ART) were made using Madsen ZO 2020 set. The comparison of ART findings, particularly the interval between tonal audiometric threshold and stapedius reflex threshold, helped to diagnose cochlear location of hearing impairment in 17 subjects (15.2%) and extracochlear in 70 (62.5%) out of all the examined subjects. The analysis of the study results has confirmed the usefulness of impedance audiometry also when patients' simulation has to be excluded in the case of their claiming compensation for occupational hearing loss.

With the current epidemic of compensation claims for occupational noise-induced hearing loss, the number of claimants in whom hearing test results do not reflect the true hearing status still inexorably increase. The incidence of a such cases with feigned hearing loss is reported at between 20 and 25 per cent of all patients being tested. Searching for any reliable indicators useful in uantifying a valid hearing thresholds the authors present their own experience with the electric response audiometry (ERA) by the use of the Amplaid MK 10 system a series of 56 malingerers. A suggested test protocol including the click-evoked auditory brainstem responses (ABR) and the 40 Hz logon-evoked middle latency responses (MLR) is discussed as a promising method for determining a frequency-specific threshold.

The periodical audiometric examinations carried out in order to identify persons with high susceptibility to acoustic trauma is very important in the hearing protection projects concerning workers occupationally exposed to noise. The authors present a computerized system which allows collection and analysis of the results of medical and audiometric examinations. Computer analysis of audiometric data helps to select and protect the workers with dynamic progression of hearing impairment. We believe that the hearing protection system we propose may improve medical care for the workers at risk.

It is well known that exposure to intense acoustic stimuli can induce permanent damage to the tissues of the inner ear. In this study the technique of ABR measurement and the experimental animal model of acoustic trauma were presented. In forty 3 months old guinea pigs the hearing threshold was assessed using the ABR technique (Amplaid mk 10 system). The hearing thresholds ranged from 40 to 50 dB-pe-SPL (mean 45.26 dB, sd. 4.73). The mean latencies of the four most prominent peaks in the ABR pattern were also measured. Fourteen of animals were then exposed to a 1 kHz pure tone at different duration and stimulus level. The ABR threshold was measured immediately after exposure and 20 to 30 days later. The exposure at 112 dB for 2h caused the threshold shift in all guinea pigs varying from 25 to 65 dB. After 3-4 weeks of recovery time in all animals hearing threshold improved, in some animals reaching the pre-exposure level. We conclude that the ABR technique allows to measure precisely and with high reproducibility the hearing level in guinea pigs and also allows to estimate the threshold shift after exposure to noise.