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Objective: It has been shown that oxidative stress plays an important role in development of noise induced hearing loss. Since static magnetic fields (SMF) exposure may alter dynamics of oxidative processes in the tissue, the aim of the study was to assess the influence of SMF on noise-induced alteration in the cochlear level of reactive oxygen species (ROS) and hearing thresholds., Materials and Methods: Auditory brainstem response (ABR), lipid peroxidation (LPO) levels, super-oxide dismutase (SOD) activity and catalase activity were assessed in the cochlea prior to, and at five time-points over two weeks following exposure of C57BL/6 mice to 8h, 119 dB SPL, 4 kHz octave band noise., Results: The ABR indicated no permanent functional damage due to noise exposure either for the 4 kHz and 8 kHz SMF-exposed group or for animals not exposed to SMF. However, significant differences in LPO level, catalase and SOD activity between animals exposed to noise and SMF and those exposed to noise only were observed., Conclusions: The results suggest that SMF causes an increase in ROS level in the cochlea after noise exposure and, at the same time, it speeds up activation of antioxidative enzymes.

Objective: To assess the usefulness of acoustic analysis with vocal loading test for evaluating the treatment outcomes in occupational voice disorders., Methods: Fifty-one female teachers with dysphonia were examined (Voice Handicap Index--VHI, laryngovideostroboscopy and acoustic analysis with vocal loading) before and after treatment. The outcomes of teachers receiving vocal training (group I) were referred to outcomes of group II receiving only voice hygiene instructions., Results: The results of subjective assessment (VHI score) and objective evaluation (acoustic analysis) improved more significantly in group I than in group II. The post-treatment examination revealed a decreased percentage of subjects with deteriorated jitter parameters after vocal loading, particularly in group I., Conclusions: Acoustic analysis with vocal loading test can be a helpful tool in the diagnosis and evaluation of treatment efficacy in occupational dysphonia.

Introduction: Teachers are at risk of developing voice disorders. A clinical battery of vocal function tests should include non-invasive and accurate measurements. The quantitative methods (e.g., voice acoustic analysis) make it possible to objectively evaluate voice efficiency and outcomes of dysphonia treatment., Materials and Methods: To identify possible signs of vocal fatigue, acoustic waveform perturbations during sustained phonation were measured before and after the vocal-loading test in 51 professionally active female teachers with functional voice disorders, using IRIS software. All the participants were also subjected to laryngological/phoniatric examination involving videostroboscopy combined with self-estimation by voice handicap index (VHI)-based scale., Results: The phoniatric examination revealed glottal insufficiency with bowed vocal folds in 35.2%, soft vocal nodules in 31.4%, and hyperfunctional dysphonia with a tendency towards vestibular phonation in 19.6% of the patients. In the VHI scale, 66% of the female teachers estimated their own voice problems as moderate disability. An acoustic analysis performed after the vocal-loading test showed an increased rate of abnormal frequency perturbation parameters (pitch perturbation quotient (Jitter), relative average perturbation (RAP), and pitch period perturbation quotient (PPQ)) compared to the pre-test outcomes. The same was true of pitch-intensity contour of vowel /a:/, an indication of voice instability during sustained phonation., Discussion and Conclusions: The recorded impairments of voice acoustic parameters related to vocal loading provide further evidence of dysphonia. The voice acoustic analysis performed before and after the vocal-loading test can significantly contribute to objective voice examinations useful in diagnosis of dysphonia among teachers.

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.

Objectives: The aim of the study was to recommend methods for assessing low frequency noise (LFN) in the occupational environment to prevent annoyance and its effects on work performance. Three different evaluating methods and corresponding admissible values were proposed: (i) method I--frequency analysis in 1/3-octave bands within the range of 10-250 Hz, (ii) method II--consisting in 1/3-octave band measurements and determination of low frequency equivalent-continuous A-weighted sound pressure level (SPL) in the frequency range of 10-250 Hz, and (iii) method III--based on equivalent-continuous A-weighted SPL corrected due to the presence of low frequencies and tonal character of LFN. Separate noise limits were recommended for workplaces in control rooms and office-like areas., Materials and Methods: The proposed criteria were verified in laboratory and field studies. The laboratory study included 55 volunteers, aged 21.8 +/- 2.1 years, with normal hearing (< 25 dB HL). The subjects listened to different noises at A-weighted SPL of 45-65 dB, and evaluated annoyance using a 100-score graphical rating scale. In the field study, 35 male workers, aged 40.1 +/- 7.2 years, exposed to LFN at A-weighted SPL of 48-61 dB, were asked to rate noise annoyance at their workplaces using a similar graphical scale. The subjective ratings of LFNs were compared to objective results from various assessing methods. The relations between annoyance and excesses of proposed limits were analyzed using Pearson's correlation coefficient (r)., Results: Linear relationships between the subjective ratings and results from all proposed exposure criteria were observed (0.550 < or = r < or = 0.673; p < 0.001). In the field conditions, however, the highest correlation coefficient was found for method II (r = 0.673), while during the laboratory study for method I (r = 0.612) and criterion curves based on hearing threshold level (HTL)., Conclusions: All proposed criteria, especially the evaluation method based on the low frequency equivalent-continuous A-weighted sound SPL (method II) as well as the frequency analysis in 1/3-octave bands 10(20)-250 Hz (method I) and criterion curves based on HTL or A-weighting characteristics, seem to be able to quite well predict annoyance experienced from LFN at workplaces.

Objectives: There is a growing body of data showing that low frequency noise (LFN), defined as broadband noise with dominant content of low frequencies (10-250 Hz) differs in its nature from other environmental noises at comparable levels. The aim of the study was to investigate whether exposure to LFN at levels normally occurring in the industrial control rooms can influence human mental performance (e.g., visual functions, concentration, continuous and selective attention) and subjective well-being., Materials and Methods: The study included 96 female and male volunteers, aged 19-27 years, categorized in terms of sensitivity to LFN. They worked with four standardized psychological tests (Signal Detection, Stroop Color-Word, Comparing of Names, and Continuous Attention) during exposure to LFN or broadband noise without dominant low frequency content (reference noise) at a level of 50 dB(A). Each subject was studied only once at randomly-assigned exposure conditions., Results: In the Comparing of Names Test, the subjects, regardless of the LFN sensitivity, showed tendency to make more errors during exposure to LFN than in the reference noise, and in the Signal Detection Test, they generally reacted faster (had shorter median detection time). In those noise conditions, however, the high-sensitive to LFN subjects, showed tendency to work less precisely (achieved lower number of correct responses in the Signal Detection Test) compared with the low-sensitive ones, while in the reference noise there was no difference related to noise sensitivity. The subjects categorized as high-sensitive to LFN also showed poorer performance than others during exposure to LFN in the Stroop Color-Word Test (a significant interaction between noise and noise sensitivity in case of reading interference index) and in the Continuous Attention Test (a tendency to more erroneous reactions)., Conclusions: These findings suggest that LFN at moderate levels might adversely affect visual functions, concentration, continuous and selective attention, especially in the high-sensitive to LFN subjects.

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.

Objectives: It has been shown that low frequency noise (LFN), defined as broadband noise with dominant content of low frequencies (10-250 Hz), may be annoying to exposed subjects. The aim of the study was to compare the degree of annoyance caused by LFN with that caused by broadband noise (BBN) without dominant low frequency components at similar A-weighted sound pressure levels., Materials and Methods: Subjects included in the study were 145 male employees of the control rooms. They were exposed to noise through headphones at gradually increasing dB A-weighted sound pressure levels within the range of 62-84 dB. Annoyance rating was based on a 100-score graphical scale., Results: LFN was rated as significantly more annoying than BBN at the comparable A-weighted sound pressure levels. The annoyance assessment of either noise did not depend on age, length of employment or the level of exposure to noise at a current workplace., Conclusions: LFN represents a higher risk of influencing human well-being than regular BBN and should be considered in the occupational exposure assessment.

Objectives: A widespread use of mobile phones evokes a growing concern for their possible adverse effects on the human central nervous system. This study was aimed at evaluating the effects of EMF generated by mobile phones, at all standard wavelengths: 450, 935 and 1800 MHz used in Poland, on the auditory brainstem-evoked responses (ABR) during and after the exposure., Materials and Methods: The effects of acute exposure to electromagnetic fields (EMF) on ABR were evaluated in 45 young, healthy volunteers of both genders. The electromagnetic impulses were generated with the antenna of mobile phone. The exposure was induced by repeated phone activation for 20 min. The ABR evaluation was performed before, during and immediately after the exposure, and the latencies of waves I, III and V, and inter-waves I-V were analyzed., Results: Prior test calibration on a phantom did not show the influence of the external EMF generated by the mobile phone on the ABR equipment. For neither EMF frequency, differences were observed in wave and inter-wave latencies during and after exposure to EMF compared to the initial ABR pattern, in both men and woman., Conclusions: This implies that commonly used mobile phones do not affect propagation of electrical stimuli along the auditory nerve to auditory brainstem centers.