Evaluating D-methionine dose to attenuate oxidative stress-mediated hearing loss following overexposure to noise.

Noise exposure causes an excessive reactive oxygen species (ROS) generation as an unwanted byproduct of high metabolic activity. Oxidative stress and antioxidative protective mechanisms have been therefore proposed as the most interesting issues in the development of noise-induced hearing loss. The aim of this study was to examine changes in superoxide dismutase (SOD), catalase (CAT) and the auditory brainstem response (ABR) in the cochlea of C57BL/6 mice 1, 7 and 14 days after exposure to 4 kHz octave band noise at the intensity of 110 dB SPL for 8 h. The evaluation of three D-methionine (D-met) doses (100, 200 and 400 mg/kg) has been performed in order to choose an optimal concentration displaying most effectively its antioxidant and thereby otoprotective functions. Administering D-met at the dose of 400 mg/kg resulted in a significant decrease in threshold shift (TS) independently of the evaluation time after exposure to noise. SOD activity was strongly supported by the same concentration (400 mg/kg) of D-met. This effect was seen not shortly, but 7 and 14 days after exposure to noise. CAT activity was induced only by noise and it reached the peak levels 7 days after exposure. D-Met at the doses of 200 and 400 mg/kg significantly decreased noise-induced changes in CAT activity. The findings of this study indicate that the protective effect depends on the concentration of D-met and can be fully expressed only when the drug is administered in the dose 400 mg/kg.

Correlation between acoustic parameters and Voice Handicap Index in dysphonic teachers.

OBJECTIVE: The aim of this study was to investigate the relationship between acoustic analysis and biopsychosocial implications of voice problems, evaluated by the Voice Handicap Index (VHI). MATERIALS AND METHODS: The study comprised 120 female teachers with voice disorders, evaluated by videolaryngostroboscopy. 60.8% of this group were diagnosed as having functional dysphonia and 39.2% had dysphonia with benign vocal fold masses (nodules and polyps). The controls consisted of 30 euphonic women. The correlations between VHI and acoustic analysis were assessed in both groups using the Pearson correlation coefficient and regression analysis. RESULTS: In teachers, the total VHI score was over 5 times as high as in controls (p < 0.001). Moreover, in teachers, significant positive correlations were found between the total VHI score and the frequency perturbation parameters and amplitude perturbation parameters when both statistical methods were used. These acoustic parameters also significantly correlated with the score on the functional and emotional subscales, but rarely with the physical subscale of the VHI. CONCLUSIONS: The study revealed a significant relationship between the objective voice measurements and the VHI. The results confirmed that VHI can be a valuable tool for assessing biopsychosocial implications of occupational dysphonia and should be incorporated in multidimensional voice evaluation.

Candidate gene association study for noise-induced hearing loss in two independent noise-exposed populations.

Millions of people are daily exposed to high levels of noise. Consequently, noise-induced hearing loss (NIHL) is one of the most important occupational health hazards worldwide. In this study, we performed an association study for NIHL based on a candidate gene approach. 644 Single Nucleotide Polymorphisms (SNPs) in 53 candidate genes were analyzed in two independent NIHL sample sets, a Swedish set and part of a Polish set. Eight SNPs with promising results were selected and analysed in the remaining part of the Polish samples. One SNP in PCDH15 (rs7095441), resulted in significant associations in both sample sets while two SNPs in MYH14 (rs667907 and rs588035), resulted in significant associations in the Polish sample set and significant interactions with noise exposure level in the Swedish sample set. Calculation of odds ratios revealed a significant association of rs588035 with NIHL in the Swedish high noise exposure level group. Our studies suggest that PCDH15 and MYH14 may be NIHL susceptibility genes, but further replication in independent sample sets is mandatory.

The effectiveness of voice therapy for teachers with dysphonia.

OBJECTIVE: An incorrect voice emission is a risk factor for developing occupational voice disorders. The study aimed at assessing the effectiveness of voice therapy in female teachers with dysphonia. METHODS: The study comprised 133 subjects with voice disorders, taking part in a vocal training programme. A reference group for the present study included 53 teachers with dysphonia. Questionnaire surveys, phoniatric examination and videostroboscopic evaluation were conducted at initial and control examination. RESULTS: In the study group, an improvement after the vocal training was noted in most of the reported symptoms and also in some quantitative parameters of phoniatric examinations compared to the findings for the reference group. The number of patients who assessed their voice as normal increased significantly after the vocal training (2.3 vs. 46.6%). A significant increase in the mean maximum phonation time, from 13.3 to 16.6 s, was observed. The same applied to voice frequency range (increase from 171 to 226.8 Hz). CONCLUSIONS: The outcomes of vocal training, such as a subjective improvement of voice quality and an increase in the quantitative parameters (prolonged maximum phonation time, extended voice range) seem to be important parameters for monitoring the effectiveness of training in correct voice emission.

Noise-induced time-dependent changes in oxidative stress in the mouse cochlea and attenuation by D-methionine.

Oxidative stress in the cochlea is considered to play an important role in noise-induced hearing loss. This study determined changes in superoxide dismutase (SOD), catalase, lipid peroxidation (LPO) and the auditory brainstem response (ABR) in the cochlea of C57BL/6 mice prior to and immediately, 1, 3, 7, 10, 14 and 21 days after noise exposure (4 kHz octave band at the intensity of 110 dB SPL for 4 h). A significant increase in SOD activity immediately and on 1st day after noise exposure, without a concomitant increase in catalase activity suggested a difference in the time dependent changes in the scavenging enzymes, which facilitates the increase in LPO observed on day 7. The ABR indicated significant noise-induced functional deficits which stabilized in 2 weeks with a permanent threshold shift (PTS) of 15 dB at both 4 kHz and 8 kHz. The antioxidant D-methionine (D-Met) reversed the noise-induced changes in LPO levels and enzyme activities. It also significantly reduced the PTS observed on the 14th day from 15 dB to 5 dB for 4 kHz. In summary, the findings indicate that time-dependent alterations in scavenging enzymes facilitate the production of reactive oxygen species and that D-met effectively attenuates noise-induced oxidative stress and the associated functional loss in the mouse cochlea.

The prevalence and risk factors for occupational voice disorders in teachers.

OBJECTIVE: Occupational voice disorders in Poland account for over 25% of all occupational diseases. The aim of the study was to assess the prevalence of voice problems in the general population of Polish teachers, and identify risk factors for developing voice pathology. PATIENTS AND METHODS: The study group comprised 425 female full-time teachers (most of them primary and secondary school, age ranging from 23 to 61 years) and 83 non-teacher women (control) whose jobs did not involve vocal effort, matched for age to the study group. All participants were subjected to a survey using an extensive questionnaire, and to laryngological, phoniatric and videostroboscopic examinations. RESULTS: The overall lifetime vocal symptoms were more frequent in the teachers than in the non-teachers (69 vs. 36%), and in particular it related to permanent and recurrent hoarseness, and dryness in the throat. Mean number of the voice symptoms was 3.21 in teachers and 1.98 in controls (p < 0.001). Abnormal (non-euphonic) voice, neck muscle hypertension during phonation and incorrect resonator function were also significantly more frequent in the teachers. Mean maximum phonation time was shorter in teachers than in the controls (14.3 vs. 15.9 s, p < 0.01). Occupational voice disorders and hyperfunctional dysphonia (that is thought to predispose to such pathology) were found in 32.7% of teachers and 9.6% of control subjects. The probability of developing incomplete glottal closure (odds ratio 13.2x; 95% CI: 1.8-96.8) and hyperfunctional dysphonia (odds ratio 2.7; 95% CI: 1.14-6.44) were significantly higher in the teacher group versus non-teachers. A significant positive relationship was found in teachers between the prevalence of hyperfunctional dysphonia and strained phonation, neck muscle hypertension, instability of voice, self-assessed hyper-arousal, and lifetime vocal effort index (years of employment as a teacher x hours of professional activity/week). The prevalence of vocal nodules and incomplete glottal closure were correlated with incorrect phonation technique parameters, but not with psychological factors. No correlation was found with environmental variables, such as classroom temperature, humidity, airborne dust. CONCLUSION: The prevalence of self-reported symptoms and clinical signs of voice disorders is around 2-3 times more frequent in Polish female teachers than in non-teachers. Lifetime vocal effort, incorrect technique of phonation and psychological predisposition seem to constitute major risk factors for developing occupational voice disorders.

[Verified maximum admissible intensity (MAI) values for the ultrasonic noise in work environment]. / Nowelizacja wartosci najwyzszych dopuszczalnych natezen (NDN) halasu ultradzwiekowego w srodowisku pracy.

The measurement methods and occupational exposure limits for ultrasonic noise (airborne ultrasound) are described. Typical sources of ultrasonic noise and sound pressure levels measured at workplaces are discussed. The verified Polish regulations on maximum admissible intensity (MAI) values for ultrasonic noise in the work environment and proposals of exposure limits for workers at particular risk (i.e. pregnant women and juveniles) are presented.

Hearing loss among workers exposed to moderate concentrations of solvents.

OBJECTIVES: It is known that some industrial organic solvents are ototoxic. This study was aimed at evaluating the hearing effects of a mixture of organic solvents alone or in combination with noise on employees in paint and lacquer enterprises. The concentration of solvents was below the occupational exposure limits (OEL) for most of the subjects. METHODS: Altogether 517 subjects were divided into the following three groups: persons with no risk due to noise or organic solvent exposure at the workplace, workers exposed to organic solvents only, and workers exposed to both organic solvents and noise. RESULTS: The relative risk (RR) of hearing loss in the solvent-only exposure group was significantly increased (RR 4.4 and RR 2.8 for noise exposure of < 80 dB-A and < 85 dB-A, respectively) in a wide range of frequencies (2-8 kHz). No additional risk in the solvent + noise exposure group was found (RR 2.8). Hearing thresholds were significantly poorer in a wide range of frequencies (1-8 kHz) for both groups exposed to solvents, when compared with the reference group. The mean hearing thresholds at frequencies of 2-4 kHz were poorer for workers exposed to solvents + noise than for the solvent-only group; this finding suggests an additional effect for noise. However, there was no correlation between hearing loss and the extent of solvent exposure. CONCLUSIONS: The results indicate that occupational organic solvent exposure at moderate concentrations increases the risk of hearing loss, and the ototoxic effects should be considered when the health effects of exposed workers are monitored.

[Hearing impairment in the plastics industry workers exposed to styrene and noise]. / Ocena uszkodzen sluchu u pracowników narazonych na styren i halas w przemysle tworzyw sztucznych.

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.

[Standardized new method for measuring vibration perception]. / Standaryzacja nowej metodyki badania czucia wibracji.

The examination of the vibration perception is one of the basic measurements applied in the evaluation of the peripheral neuropathies in hand-arm vibration syndrome (HAVS) The detailed guidelines on how this kind of examinations should be performed, presented in the 1998 ISO standard, differ substantially from those currently binding in Poland. The aim of this study was to standardize the method of vibration perception measurements, taking account of the parameters consistent with the ISO recommendations, such as algorithm (stimulus presentation method), vibration frequency, the size and contact force of vibrating probe, as well as the comparison of the results obtained by means of both methods (ISO-recommended method and standard Polish method). It was found that the algorithm change (ascending method replaced by Bekesy's technique, recommended by ISO) did not affect the of the vibration perception thresholds values within the wide range of frequencies (32-500 Hz), whereas the decreased size of probe, pressed with smaller contact force, resulted in significantly higher values of perception thresholds within the frequency range of 125-400 Hz. The comparison of the outcomes of the ISO-recommended and Polish standard methods revealed that the perception thresholds did not differ at the frequency of 125 Hz, but at the frequencies of 250 and 400 Hz, the ISO-recommended method produced higher values. Moreover, at the frequencies ranging from 125 to 400 Hz, the results of the perception threshold measurements, taken several times in the same persons (intrasubject variability) by means of both methods, were more scattered. It was revealed that the measurements at the frequency range of 4-125 Hz should be included in the vibration perception examinations, and the certification of the ability to work in the conditions of exposure to hand-arm vibration should be based on their results. It is also essential that in the standard examination, a smaller vibratory probe (phi = 5 mm) and lighter contact force (0.1 N) than those currently used, should be applied.

[Revised maximum admissible intensity (MAI) values for infrasonic noise in work environment]. / Nowelizacja wartosci najwyzszych dopuszczalnych natezen (NDN) halasu infradzwiekowego w srodowisku pracy.

A short review of infrasound sources is presented. The measuring methods and occupational exposure limits for infrasonic noise (infrasound) are described. The amended Polish regulations on maximum admissible intensity (MAI) values for infrasonic noise in work environment and proposals of exposure limits for workers at particular risk (i.e. pregnant women and juveniles) are discussed.

Hair cell regeneration in the chick basilar papilla after exposure to wide-band noise: evidence for ganglion cell involvement.

It has been demonstrated that the auditory epithelium in the chick basilar papilla may regenerate after acoustic or ototoxic damage. Both types of damage may elicit the appearance of new cells that may develop in to the sensory cells. Factors inducing this process and the role of ganglion cells, the first neuron cells in the auditory pathway, are still unknown. The pattern of auditory damage and regeneration, after octave-band and pure-tone noise exposure, has been well established in research studies on chicks, but there are scarce data on wide-band noise effects. The aim of this study was to investigate the effect of wide-band noise, with different exposure levels applied, on the chick basilar papilla and supporting cells. Further, it was also aimed to determine whether the proliferation of ganglion cells, after wide-band noise exposure, occurs. The morphological changes were assessed with fluorescent, light, and transmission electron microscopy. Cell proliferation was studied based on immunoreactivity assays of proliferating cell nuclear antigen (PCNA). The exposure to wide-band noise at 120 dB SPL for 72 h produced stripe-like lesion of tall hair cells along the neural edge of the basilar papilla, mainly in the middle and, at the lesser extend, in its proximal part. There was no patch-like damage to the region of short hair cells, commonly observed after the exposure to the octave-band or pure-tone noise. The lesion extend depended on the level of exposure. The lower equivalent levels of noise (120 dB SPL for 40 h intermittent exposure) produced proportionally less damage. No morphological changes at light and fluorescent microscopy (apart from tectorial membrane exfoliation) were observed at 110 dB SPL in case of 20 h intermittent exposure. The elimination of dying hair cells took place either by pulling a damaged cell down to the basilar membrane or by extruding the cell to the subtectorial space. New hair cells reappeared at the sensory epithelium on the fifth day after the end of exposure. Cell proliferation started prior to hair cell loss. PCNA-like immunoreactivity was observed after the exposure at all levels in both the damaged and intact areas. PCNA appeared not only in the supporting cells, as indicated in previous studies, but also in the ganglion cells, suggesting ganglion cell involvement in the process of regeneration.

[Assessment of hearing impairment in workers exposed to mixtures of organic solvents in the paint and lacquer industry]. / Ocena uszkodzen sluchu u pracowników narazonych na mieszaniny rozpuszczalników organicznych w przemysle farb i lakierów.

Clinical and experimental studies indicate a possible harmful effect of chemicals, especially organic solvents, on the hearing system. In combined exposure to noise and solvents, very common in industry, it is most likely that a synergetic action of these factors enhances the traumatising effect of exposure to noise. The aim of this study was to assess the incidence and the risk of hearing impairment in 117 paint and lacquer factory workers exposed to a mixture of organic solvents. An analysis of organic solvent mixtures reveals that xylene and ethyl acetate are their major components whose concentrations depend on individual workposts. The control group consisted of 76 workers exposed to noise exceeding, Threshold Limit Value and 125 healthy subjects exposed neither to noise nor to solvents in their occupational setting. Pure tone audiometry revealed the highest hearing thresholds in workers exposed to solvents, lower thresholds in those exposed to noise, and the lowest ones in the non-exposed individuals. Hearing loss was found in 30% of workers exposed to organic solvents, in 20% of noise-exposed subjects, and in only 6% of non-exposed subjects. The comparison of relative risk values also indicated significantly enhanced probability of hearing impairment in workers of the paint and lacquer factory (9.6; 3.2-25.6), which is even more strongly pronounced than in the group of subjects exposed to noise (4.2; 1.2-13.2). An analysis of hearing impairment risk in particular frequencies suggests that organic solvents may damage the inner ear in much greater extent than noise. The results of the study show that exposure to organic solvents may create a significant risk of hearing impairment. Therefore, further steps should be taken to include the exposed population into effective preventive programmes.

[Evaluation of voice quality in students from teaching colleges]. / Ocena stanu narzadu glosu u studentów szkoly pedagogicznej.

Vocal disorders are very common occupation-related disease in teachers. Their remarkable incidence might be associated with inappropriate techniques of speech and poor vocal hygiene. The aim of this study was to assess the function of vocal organ including voice emission technique in persons starting their teaching occupation. The study group included 66 female students at Teaching College. Their were thoroughly interviewed and subjected to laryngological, phoniatric and videostroboscopic examinations. All subjects reported subjective symptoms after vocal effort. Hoarseness and throat dryness were the most common. In the majority of students functional vocal disorders were observed. In 30% of them insufficiency of glottis and in four (6.1%) students soft vocal nodules were found. Signs and symptoms of vocal diseases were more frequent in a subgroup of students exposed to increased vocal effort during their professional education. The results indicate that young teachers are not sufficiently prepared for increased vocal strain, apparently associated with their profession. It is indeed necessary to introduce preventive programs including special training of appropriate speech technique, into the curricula of schools for teachers.

[Hair cell regeneration in a chicken's inner ear after damage due to exposure to industrial noise]. / Ocena regeneracji komórek rzesatych ucha wewnetrznego kurczecia uszkodzonych przez halas przemyslowy.

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.

[Otoacoustic emission nonlinear distortions in musicians with absolute and relative pitch]. / Otoemisje znieksztalcen nieliniowych u muzyków ze sluchem absolutnym i relatywnym.

In the presented study an analysis was performed of the properties of the cochlea using Distortion Product Otoacoustic Emissions (DPOAE). 52 musicians were examined, aged 17-31 years, with systematic musical training longer than 10 years, and 30 non-musicians without musical experience, aged 18-30 years. Then all musicians were tested with Rakowski's test to divide them into the absolute pitch possessors (APP) and relative pitch possessors (RPP). DPOAE recorded in musicians were statistically higher than in nonmusicians for f2 = 1.0, 2.0 and 4.0 kHz for signal intensities generally ranged from 45 to 55 dB SPL. Analogous comparison between APP and RPP showed higher DPOAE for f2 = 2.0 and 4.0 kHz in APP but the differences were not statistically significant. Simultaneously no significant differentiations were observed between investigated groups for highest signal intensities in the whole frequency band. The study suggests that systematic musical training influences the cochlear mechanics assessed by DPOAE and the greatest differences concern the active processes within the cochlea. The continuation seems to be justified.

[The application of otoacoustic emissions measurement in the assessment of the function of cochlear efferent fibers: the study of normal hearing subjects]. / Zastosowanie pomiarów emisji otoakustycznej do oceny funkcji ukladu eferentnego slimaka--badania osób z prawidlowym sluchem.

It has been shown by L. Collet in 1990 that the contralateral noise stimulation causes the decrease in the amplitude of otoacoustic emissions in the ipsilateral (tested) ear. This effect is linked to the activation of crossed efferent fibres in the cochlea. This non-invasive method is becoming a useful tool in assessing the function of efferent system in human. In this study the effect of contralateral noise stimulation was assessed in 10 young subjects with normal hearing. The contralateral stimulation caused the decrease in the amplitude of both transient evoked otoacoustic emission (TEOAE) and distortion-product otoacoustic emission (DPOAE) in the majority of tested ears. The statistically significant effect was observed already at the intensity of noise of 40 dB (A). At the lower level of noise (30 dB-A) the small increase in the amplitude of otoacoustic emissions in some ears was observed. The suppressive effect of contralateral stimulation depended clearly on the intensity of noise; the higher intensity of noise, the greater suppressive effect was seen. However, the decrease in the otoacoustic emissions was very small (usually in the range from 1 to 2 dB), which may limit practical application of this method in the assessment of the function of efferent system.

[Environmental exposure to electromagnetic fields and the risk of cancer]. / Ekspozycja srodowiskowa na pola elektromagnetyczne a ryzyko rozwoju chorób nowotworowych.

Electromagnetic fields (EMFs) of power-line frequency are very common in the human environment. Electric tractions and transmission lines of high voltage are their major sources, however, household appliances are also involved in generating EMFs. Although their biological effect has not as yet been well documented, they evoke an increasing concern as being suspected of their carcinogenic effect. This concern arises mainly from epidemiological studies, which indicate an increased risk for leukemia in children living in the vicinity of transmission lines of high voltage. The author presents a review of epidemiological and experimental studies on a possible effect of power-line frequency EMFs on the development of neoplastic diseases. Epidemiological data obtained to date shows that power-line frequency EMFs do not induce cancer risk and if this is the case the risk is marginal (relevant risk of 1-4 order). Nevertheless, this risk seems to be more evident in occupational than in environmental exposure. The results of experimental studies carried out on animals disclose a possible effect of EMFs as a factor contributing to the development of cancer induced by a known carcinogen. In order to answer the question put in the title it is necessary to continue a large scale investigations especially experimental ones.

The morphological structure of the chick's basilar papilla: a light and transmission electron microscopic study.

The basilar papilla corresponds to the cochlea of mammals and is becoming a common model of assessment of the regeneration process which takes place after the damage to the inner ear caused by noise or ototoxic drugs. In this study the morphology of a chick's basilar papilla in light and electron microscopy is described. There are two types of hair cells (sensory cells): the tall hair cells and the short hair cells, whose morphology and pattern of innervation are different. The tall hair cells correspond to the inner hair cells in mammals, which are responsible for sound transduction. They are mainly innervated by the afferent (cochlear) fibers. The short hair cells correspond to the outer hair cells in mammals, which are responsible for the sound amplification. They are mainly innervated by the efferent fibers. The supporting cells, whose morphology is also described in the study, separate the hair cells from each other and from the basilar membrane. They are considered to be a source for regenerating hair cells.

[Is otoacoustic emission useful in the differential diagnosis of occupational noise-induced hearing loss?]. / Czy emisja otoakustyczna moze byc przydatna w diagnostyce róznicowej zawodowych uszkodzen sluchu?

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.