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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.

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 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.

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.

The aim of the study was to assess and compare click-evoked otoacoustic emissions (e-OAE) and distortion product otoacoustic emissions (DPOE) in normally hearing subjects. The study was conducted on 48 ears in adults (12 women and 12 men; the age ranging from 16 to 40 years). E-OAE and DPOE was present in all examined ears. The amplitude of e-OAE ranged from 3.4 to 23.5 dB SPL (mean 11.7 +/- 4.95 dB SPL). In women the mean amplitude was slightly higher than in men. Spectral analysis of e-OAE revealed the highest level of otoacoustic emissions at the frequency 1000 Hz and significant decrease e-OAE at frequencies above 4500 Hz. DPOE were registered within the range of frequencies from 700 to 6000 Hz. Thus, DPOE allowed to measure otoacoustic emissions additionally in the high frequency region. We found significant variability in DPOE detection thresholds ranging from 25 to 70 dB SPL. Both types of otoacoustic emissions revealed significant inter-subject variability and very good test-retest repeatability. We conclude that both measurements allow to assess the function of the cochlea in the frequency specific regions, but DPOE, because of using pure tones stimuli, is more specific. The reference-values for adults are presented in this study.

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 authors present some morphological, physiological and pathophysiological aspects of efferent system of innervation (i.e. olivocochlear system) of the organ of Corti. The cochlea is innervated by two different systems: 1) the medial efferent system which originates in the medial nucleus of the trapezoid body and synapses on outer hair cells, 2) the lateral efferent system which originates in the superior olivary nucleus and synapses on the dendrites of the auditory nerve under inner hair cells. An electrical stimulation as well as an acoustic stimulation of efferent fibers results in: a) suppression of the auditory nerve response (N1 amplitude reduction), b) increase in amplitude of cochlear microphonics and c) reduction of the endolymphatic potential. Due to presence of the crossed olivocochlear bundle, an ipsilateral stimulation of efferent fibers results in both ipsi- and contralateral response. Efferent fibers response is a feedback response to afferent fibers stimulation. There are some evidence that efferent system of innervation protects the cochlea against the effects of intense sound exposure.

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.

The conventional bone conduction audiometry does not allow an objective assessment of hearing in patients with otospongiosis. We evaluated a new method of direct bone conduction audiometry with the stimulator applied to the promontory intraoperatively. A comparison of conventional and direct bone conduction audiometry thresholds was made in 100 patients in various stages of otospongiosis before stapedectomy. A significant correlation between hearing thresholds obtained by both methods was observed for all frequencies tested (500, 1000, 2000 and 4000 Hz). The direct bone conduction method was at least 30 dB more sensitive for all frequencies. Interestingly, the average direct bone conduction threshold curve did not exhibit a Carhart notch at 2000 Hz compared to the conventional method. We concluded that our bone conduction technique enabled a better assessment of cochlear reserve in patients with otospongiosis.

The actual "early" improvement of hearing thresholds following stapedectomy were measured in 100 patients with otospongiosis by use of direct (intraoperative promontory bone stimulation) and conventional bone conduction audiometry prior to surgery. The direct bone conduction technique was usually more predictive in hearing improvement following stapedectomy than conventional bone conduction audiometry. The direct bone conduction seems to be a superior method for assessing hearing in patients with severe otospongiosis compared with conventional bone conduction which does not reflect actual cochlear reserve.