The effect of impulse noise exposure on distortion product otoacoustic emissions in the awake guinea pig.

Distortion product otoacoustic emissions (DPOAE) are a sensitive detector of outer hair cell (OHC) function and were monitored in awake guinea pigs before and after impulse noise damaging the cochlea (peak intensity 153 dB SPL, rise time < 0.1 ms). Animals had stable DPOAE levels before noise exposure. In the first hours after noise exposure DPOAE levels were reduced significantly. Three different patterns of recovery of DPOAE were seen in the post-exposure period:restitution exceeding controls, partial recovery and no recovery. In general, DPOAE levels declined and types of recovery closely corresponded to changes in amplitudes of cochlear microphonics after noise exposure. These data suggest that the monitoring of DPOAE is a suitable method for diagnosing impaired OHC function.

Degeneration of the hearing nerve and its detection by distorted-speech testing.

A detailed description of the physiology of the auditory system (including new essential knowledge) is provided, followed by the description of five morphological levels of acoustic signal analysis, of which four play a significant part in establishing the selection capacity of human hearing. As an essential phenomenon connected with loss of the analyzing capacity of the ear, ascending degeneration of the afferent nerve fibers of the inner hair cells and of the hearing nerve (after destruction of the inner hair cells) develops. A distorted-speech test is submitted that offers a simple and easily performed calculation of a ratio, which value renders a reliable estimation of the pathological analyzing capacity of the ear caused by ascending degeneration. The test is recommended as a reliable basic component of an audiometric battery of tests.

[Sensorineural hearing loss in children starting school. Results of a representative hearing screening study]. / Sensorineurale Gehörschäden bei Schulanfängern. Ergebnisse einer repräsentativen Hörscreeninguntersuchung.

Audiograms in the 0.5-6 kHz frequency range were taken, using improved audiometric screening methods, in 2032 children, 6-7 years old, who were undergoing their pre-school medical examinations. In 151 children (7.4%), the threshold for hearing was above 20 dB for at least one frequency. Of these, 82 children (4% of the overall sample) had a hearing impairment defined as a difference of > or = 10 dB between at least one frequency (3, 4 or 6 kHz) and the mean value from 1+2 kHz. This was evaluated as a sensorineural hearing loss. Unilateral losses (lateral difference > or = 10 dB) were more common than bilateral losses (2.5% vs 1.6% of the overall sample). These unilateral hearing losses in the high-frequency range are essentially regarded as the result of playing with impulse-noise producing toys, such as toy guns with caps.

[Detection of inactivity of the auditory system in the beginning stage with the Freiburg masked speech test]. / Zur Problematik des Nachweises einer Inaktivität des auditorischen Systems im Anfangsstadium mit dem verhallten Freiburger Sprachtest.

Late-onset auditory deprivation or "inactivity" phenomenon has been reported in single cases only because it has not been possible to assemble a larger number of calculable cohorts for which all necessary details concerning individual histories are available. Subjects should not be older than 60 years of age and should have had asymmetric hearing for at least about 10 years or should have been wearers of monaurally fitted hearing aids. The development of late-onset auditory deprivation is presented in 6 single cases. All were assessed by the Freiburg speech discrimination test and the distorted Freiburg speech test, with the latter showing greater sensitivity and variability. It is of special interest that the quotient of distorted speech is reduced in subjects who have normal hearing in one ear and considerable hearing loss in the other ear (for example, in the case of unilateral microtia). This effect may be evidence for significant activation of hearing selectivity developing in the brainstem versus inactivation.

Late-onset auditory inactivity (deprivation) in persons with bilateral essentially symmetric and conductive hearing impairment.

The purpose of this investigation was to examine the effects of prolonged monaural amplification on the suprathreshold speech-recognition scores in the unaided ears of 46 persons with bilateral essentially symmetric and conductive hearing impairment and aided ears of 46 other persons with bilateral essentially symmetric and conductive hearing impairment. All subjects were less than 50 years of age. The suprathreshold speech-recognition loss scores for taped monosyllabic German PB words were analyzed. The frequency distribution of pure-tone averages was essentially equivalent for the aided and unaided ears. Although the magnitude of hearing impairment was essentially equivalent for the aided and unaided ears, the unaided ears tended to have large suprathreshold speech-recognition loss scores than the aided ears. The results are discussed in relation to theories of auditory deprivation and inactivity from monaural amplification. The clinical significance of these findings in relation to ear surgery is also discussed.

[The definition of "selectivity" in reduced speech discrimination as a sequela of peripheral perceptual damage]. / Zur Definition "Selektionsfähigkeit" bei erschwertem Sprachverstehen als Folge peripherer Perzeptionsschäden.

The term "selectivity" means the ability to correctly select speech in the presence of other kinds of noise. In the literature the term "selectivity" is used very differently with regard to the different levels of the hearing system. In actual practice a separation of this term is important for possible audiometric topodiagnosis study. The problems of selectivity in hearing are discussed and different terms are proposed regarding the different planes of hearing system: 1. for the interaural-external ear transfer function, the terms "stereophonic outer ear effect" or "stereophonic outer ear efficiency" are used; 2. for the power of the inner ear, the term "ability of analysis"; 3. for the central auditory pathways, the term "chiasmatic selectivity" or "meshing selectivity"; 4. for the cortical centre, "active selectivity." The audiometric test batteries used clinically for topodiagnosis are discussed and two examples shown to illustrate the usefulness of the distorted Freiburg Word Test for detecting "analytical ability" in cases of inner ear damage.

[Experiences with high-frequency hearing tests in the selection of personnel for noise occupations]. / Erfahrungen über das Verhalten des Hochton-Gehörs bei der Auswahl von Arbeitern für Lärmberufe.

A total of 181 persons aged between 16 and 18 were checked fully audiometrically (conventional and high-frequency audiogram). Dates of history about hereditary hearing damage, own ear diseases, noise exposure during frequent visits to discothecs or usage of Walkman etc. were ascertained by questionnaires. The evaluation of the results was carried out with the help of discrimination analysis allowing a multi-dimensional classification. As a result there could be made a sure discrimination analytic separation in persons with ear diseases during their childhood, when the high frequencies from 10 to 15 kHz were taken in. Thus the damage of the inner ear was to be found mainly on the base of the cochlea. Also in cases of hereditary influence there was to be seen a clear deminution in the high frequency area. The group of persons, who regularly went to discos (more than three times a month) as well as the group often using Walkman revealed a sure separation, when the high frequencies above 8 kHz were considered in the calculation. Altogether there could be seen an early damage more clearly in the high frequency area after ear diseases in childhood as well as a result of sound overloading than in conventional hearing area.

[The accuracy of subjective determination of auditory threshold in the range of 0.5 to 18.0 kHz using different sound transducer systems]. / Zur Genauigkeit der subjektiven Hörschwellenbestimmung im Bereich von 0.5 bis 18.0 kHz bei Benutzung unterschiedlicher Schallgebersysteme.

This paper reports on the degree of accuracy of determinations of hearing threshold in the 0.5 to 18 kHz range. As far as possible, these hearing thresholds were compared with those of ISO 389. Furthermore, the study compared determinations of hearing thresholds measured on different days. Reproducibility was very good, particularly of the high-frequency thresholds. The two types of sound transducers used here (a quasi-free field system developed by the authors and a pair of professional headphones) showed an identical transmission of frequencies and good reproducibility of the results of measurements.

[Manifestations of inactivity in unilateral hearing aid management of patients with a high degree of hearing loss]. / Zum Problem von Inaktivitätserscheinungen bei einseitiger Hörgeräteversorgung hochgradig Schwerhöriger.

Concluding from audiometrical practice using hearing aids unilaterally we could find an inactivity of the unused contralateral ear. We have investigated if it is possible to measure this inactivity by common psychoacoustic methods. We tested 92 persons with advanced combined hearing loss. We had to state that the inactivity is not measurable by mean tone hearing loss according to HAIC (0.5, 1 and 2 kHz), the percentage hearing loss according to Fowler-Sabine, the percentage of hearing loss calculated by speech-audiogram according to Boenninghaus and Röser 1973 and the value of hearing loss for speech (a1). It is only a big discrimination loss that points to the presence of inactivity. The discrimination loss was compared in two groups concerning "used" and "unused" ears. We could clearly measure the biggest discrimination loss in the group of unused ears. The clinical consequences were discussed.

[Experiences with the distorted Freiburg Speech Test--diagnosis and rehabilitation of hearing disorders]. / Erfahrungen mit dem verhallten Freiburger Sprachtest--Diagnostik und Rehabilitation von Hörstörungen.

In accordance with the description of an extended technique of distorted speech at different values - 15 dB, - 10 dB, - 5 dB and 0 dB with the plotted frequency characteristic, we used the procedure with different kinds of sensorineural hearing loss. The method analyse the peripheral hearing system very simply. In cases of acoustic tumours the quotient is very large and it is better to reduce the degree of distortion (-10, -5 and 0 dB). Generally, it is possible to detect the phase of degeneration of the inner hair-cells and afferent nerve fibres in all cases of sensorineural hearing loss. The test is also of very good help in fitting hearing aids because method picks out the hard hearing persons with very disturbed discrimination of speech.

High-frequency audiometry in the evaluation of critical noise intensity.

We investigated a total of 537 subjects (68 men, 469 women) working in the textile industry to ascertain their hearing level in the conventional hearing range as well as in the high-frequency (HF) range. The persons we tested work at three different noise-levels [80-84, 85-89, 90-94 dB (A), measured as leq). The differences in the hearing thresholds between this three groups mentioned were checked by means of discriminant analysis. The first hearing level changes at a noise-level below 90 dB (A) leq develop mainly in the HF range. In the conventional hearing range, however, the hearing levels remain unchanged even over long exposure times. Noise-induced hearing loss in the conventional range occurs only in the sound level group of 90 to 94 dB (A) leq without attaining any social importance. The tests show that, if the noise-level 90 dB (A) leq is not exceeded, no noise-induced hearing impairments involving social hearing loss are to be observed. Thus we assume that an auditory risk criterion of 85 dB (A) leq is sufficient to prevent hearing loss of any social importance.

[High-frequency audiometry for the early diagnosis of occupational acoustic trauma]. / Einsatz der HF-Audiometrie zur Früherkennung berufsbedingter Lärmhörschäden.

We investigated a total of 537 patients (68 men, 469 women) working in the textile industry to ascertain their hearing level in the conventional hearing range as well as in the HF range. The persons tested work at 3 different noise levels (80-84, 85-89 and 90-94 dB [A] Leq). The differences in the hearing thresholds of the three sound level groups mentioned above were checked by means of discrimination analysis. The first hearing level changes noise levels below 90 dB develop mainly in the HF range; in the conventional hearing range, however, the hearing levels remain unchanged even during long exposure times. Hearing level impairment in the conventional range occurs only in the sound level group of 90-94 dB (A) Leq without attaining any social importance. The tests clearly show that if the noise level damage risk criterion of 85 dB (A) Leq at which hearing is impaired, is not exceeded any hearing lesions involving social hearing loss are definitely avoided.

[Assessment of social hearing with a questionnaire in relation to average hearing loss]. / Zur Einschtzung des Sozialgehörs mit Fragebogen in Relation zum mittleren Hörverlust.

In 86 patients with sensorineural hearing loss we checked if the measuring results obtained by conventional audiometric procedures correlate with the subjective impression of hard hearing ascertained via a special questionnaire. For this purpose we compared the average hearing loss (500, 1000, 2000 Hz) of the puretone audiogram with the results obtained via the questionnaire developed by v. Wedel and Tegtmeier for assessing the social hearing handicap (SHH). We can see that there is good correlation between the SHH index values and the average hearing loss with frequencies of 0.5, 1.2 kHz in pancochlear perception hearing loss, whereas in patients with basocochlear perception hearing loss the SHHI cannot be calculated with the help of the puretone audiogram, nor will a widening of the frequency range up to 6 kHz lead to a better correlation between the average hearing loss and SHHI.

[The problem of critical intensity]. / Zur Problematik der kritischen Intensität.

We investigated a total of 537 patients (68 men, 469 women) working in the textile industry to ascertain their hearing level in the conventional hearing range as well as in the HF range. The persons tested work at 3 different noise levels (80-84, 85-89 and 90-94 dB (A) Leq. The differences in the hearing thresholds of the three sound level groups mentioned above were checked by means of discrimination analysis. The first hearing level changes noise levels below 90 dB develop mainly in the HF range; in the conventional hearing range, however, the hearing levels remain unchanged even during long exposure times. Hearing level impairment in the conventional range occurs only in the sound level group of 90-94 dB (A) Leq without attaining any social importance. The tests clearly show that if the noise level damage risk criterion of 85 dB (A) Leq at which hearing is impaired, is not exceeded any hearing lesions involving social hearing loss are definitely avoided.

High frequency hearing following otitis media with effusion in childhood.

78 children had been treated for secretory otitis media at the age of 4.4, on the average. At the age of 18.6, their hearing was checked by means of conventional and high frequency (HF) audiometry. In the conventional range, the average hearing level was nearly normal and no air-bone gap could be found. In HF-range, the average hearing level decreased clearly but the HF-hearing level was significantly affected only in cases in which an air-bone gap exceeding 40 dB and more had existed during the active secretory otitis.

Influence of different kinds of noise on the ear and some physiological and psychological parameters.

The reactions of the human organism to noise are complicated and difficult to separate from other stressors, with the exception of hearing damage. After thorough experimental planning and a rigorous selection of sample persons, the reaction to noise of varying structures was studied by reactions of heart rate, blood pressure, reaction time, the temporary threshold shift (TTS) of hearing and the psychological parameters "Mood" (in German "Befinden"). We found a special kind of TTS dependent on the structure o noise and no effect of physiological parameters. The psychological parameter tended to have a significant influence on individual factors.

[Distorted Freiburg Speech Test]. / Verhallter Freiburger Sprachtest.

In 107 patients with different types of hearing loss (air conduction, sensorineural and combined) we ascertained the monaural discrimination loss of monosyllables with the help of the normal and distorted Freiburg speech test. It was evident that the quotient obtained from the measured discrimination is a very good and useful measure to characterise the ability to analyse the peripheral hearing system. Compared with normal hearing individuals and patients with air conduction hearing loss or combined loss of hearing, persons with perception hearing loss show a much greater and more divergent quotient. The discrimination of distorted speech depends more on age than that of normal speech; however, it is considerably reduced from the sixth decade of life onwards. The distortion test offers the expertising the possibility of improved assessment of speech discrimination by workers in a noisy environment in case of unfavourable hearing conditions, but it is also of considerable importance in fitting hearing aids and in the diagnosis of acoustic tumours.