[The Freiburg monosyllabic speech test in noise]. / Der Freiburger Einsilbertest im Störschall.

BACKGROUND: Since 2017, the Freiburg monosyllabic speech test can be used in hearing aid evaluation with background noise in Germany. The results are used to compare the aided versus the unaided condition. However, there is currently no reference speech recognition curve for a comparison to listeners with normal hearing. OBJECTIVE: The goal is to establish a reference speech recognition curve for listeners with normal hearing and to analyze the perceptual equivalence of the test lists in continuous CCITT noise (according to Comité Consultatif International Téléphonique et Télégraphique). MATERIALS AND METHODS: The measurements were conducted at two different sites with 90 participants in total. Monosyllables and CCITT noise were presented at different signal-to-noise ratios by one loudspeaker from the front (S0N0). Individual and test-list specific discrimination functions were fitted to differentiate between the sites and among test lists. RESULTS: The reference speech recognition curve and its region of tolerance were established. Three perceptively deviating test lists (1, 3, 20) were identified. CONCLUSION: The reference speech recognition curve enables quantification of hearing difficulties with Freiburg monosyllables in noise and an estimation of the rehabilitation with hearing aids. This reference curve is only valid for frontal stimulus presentation (S0N0) and continuous CCITT noise. Perceptually deviating test lists were different to those in quiet, but partly correspond to literature data.

[Prevalence of hearing loss in Northern and Southern Germany. German version]. / Prävalenz von Schwerhörigkeit in Nord- und Süddeutschland.

BACKGROUND: The HÖRSTAT study conducted in Northwest Germany yielded hearing impairment in approximately 16% of adults according to the World Health Organization (WHO) criterion. However, the robustness of extrapolations on a national level might be questioned, as the epidemiological data were collected on a regional level. METHODS: Independently from HÖRSTAT, the "Hearing in Germany" study examined adult hearing in Aalen, a town located in Southwest Germany. Both cross-sectional studies were based on stratified random samples from the general population. Pure-tone average at 0.5, 1, 2, and 4 kHz (PTA4), the prevalence of hearing impairment (WHO criterion: PTA4 in the better ear >25 dB HL), and hearing aid provision were compared. Data from the Aalen study and HÖRSTAT were pooled (n = 3105) to extrapolate the prevalence and degree of hearing impairment for the years 2015, 2020, and 2025. RESULTS: Both studies show very similar results for PTA4. Weighted for official population statistics, the prevalence of hearing impairment according to the WHO criterion is 16.2% among adults, affecting 11.1 million persons in Germany. Due to demographic changes, the prevalence is expected to increase in the medium term by around 1% per 5­year period. With a similar degree of hearing loss, hearing aid provision differs from place to place. CONCLUSION: Adjusted for gender and age to the European Standard Population (ESP), the prevalence of hearing impairment observed both in HÖRSTAT and the Aalen sample is considerably lower than reported for international studies. Since the analysis refers to cross-sectional data only, possible cohort effects are not considered in the prevalence projection.

Prevalence of hearing loss in Northern and Southern Germany.

BACKGROUND: The HÖRSTAT study conducted in Northwest Germany found hearing impairment in approximately 16% of adults when applying the World Health Organization (WHO) criterion. However, the robustness of extrapolations to a national level might be questioned, as the epidemiological data were collected on a regional level. METHODS: Independently from HÖRSTAT, the "Hearing in Germany" study examined adult hearing in Aalen, a town located in Southwest Germany. Both cross-sectional studies were based on stratified random samples from the general population. The average pure-tone threshold shift at 0.5, 1, 2, and 4 kHz (PTA4), the prevalence of hearing impairment (WHO criterion: PTA4 in the better ear >25), and hearing aid uptake were compared. Data from the Aalen and HÖRSTAT studies were pooled (n = 3105) to extrapolate to the prevalence and the degree of hearing impairment for the years 2015, 2020, and 2025. RESULTS: Both studies yielded very similar results for PTA4. Weighted for official population statistics, the prevalence of hearing impairment according to the WHO criterion is 16.2% in adults, thus affecting 11.1 million persons in Germany. Owing to demographic changes, the prevalence is expected to increase in the medium term by around 1% per 5­year period. With a similar degree of hearing loss, hearing aid provision differs from place to place. CONCLUSION: When adjusted for gender and age to the European Standard Population, the prevalence of hearing impairment observed both in HÖRSTAT and the Aalen sample is considerably lower than reported for international studies. Since the analysis refers to cross-sectional data only, possible cohort effects are not considered in the prevalence projection.

[Test-retest reliability of the Freiburg monosyllabic speech test]. / Test-Retest-Reliabilität des Freiburger Einsilbertests.

BACKGROUND: ISO 8253-3 describes the requirements for speech tests used in audiology. One aspect is the test-retest reliability, which was here examined for the Freiburg monosyllabic speech test. METHODS: Speech recognition scores were examined for 30 listeners with normal hearing ability. All 20 lists of the Freiburg monosyllabic speech test were tested at four different presentation levels. The retest was carried out 7-9 months later. RESULTS: The test-retest reliability of the Freiburg monosyllabic speech test in this study is between 13 percentage points for a speech recognition score of 95 %, and 24 percentage points for a speech recognition score of 39 %. The measurement accuracy can be estimated using binomial distribution. CONCLUSION: The reproducibility of the results is limited by the small number of test items (20 words) in each list. This does not fulfill the requirements for speech tests in diagnostics and rehabilitation. An improvement of the test-retest reliability can be achieved using several test lists.

[Phonemic balance of the Freiburg monosyllabic speech test]. / Phonemische Ausgewogenheit des Freiburger Einsilbertests.

BACKGROUND: ISO 8253-3 [4] describes the requirements for speech tests with respect to their phonemic balance. The fulfillment of these requirements by the Freiburg monosyllabic speech test were examined. METHODS: The Freiburg monosyllables were phonologically transcribed and analyzed with respect to their structural types, vowels and consonants, as well as phonological classes, and compared to reference values. RESULTS: The phonemic distribution of the Freiburg monosyllables differs slightly from the reference values for the German language. The differences are presumably related to the restriction to monosyllabic substantives. Most test lists (except for 12) contain similar proportions of different phonem classes for vowel and consonants according to Hahlbrock and ISO 8253-3 [4]. CONCLUSION: The deviations of test lists 5, 11, and 15 in a study for perceptual equivalence cannot be explained by phonemic imbalance in comparison to other test lists. Only the lower recognition rates for test list 12 might be explained by its deviant phonemic distribution.

[Evaluation of the perceptual equivalence of test lists in the Freiburg monosyllabic speech test]. / Untersuchungen zur perzeptiven Äquivalenz der Testlisten im Freiburger Einsilbertest.

BACKGROUND: In the past, the perceptual balance of test lists for the Freiburg monosyllabic speech test (FBE) was frequently evaluated without producing consistent results. Until now, the studies used very diverse methods and did not accurately follow the standardized specifications. In this study, therefore, the perceptual equivalence of test lists was verified with a large group of participants according to the standard ISO EN 8253-3. METHODS: A total of 160  suitable otologically normal subjects were recruited at two institutions, each of whom listened to all test lists of the FBE using predefined measurement conditions. The subjects were divided in three groups depending on the transducer used for test list presentation (headphones "HDA 200" and "TDH 39", as well as free-field loudspeaker, "FF"). Lists that deviated were identified using the approaches specified in the standard. RESULTS: The reference curve for FBE was not met by any group. While the "HDA 200" group indicated 4.6 dB lower thresholds, results for the "TDH 39" and "FF" groups showed 1.2 and 2.5 dB higher thresholds, respectively. For an average speech recognition score of 44.3 %, test lists 5, 11, 12, and 15 lay outside the calculated tolerance range of 4.5 to -4.4 percent points. The same lists also deviated when calculating discrimination functions and therefore do not fulfill the criteria for perceptual equivalence. DISCUSSION: In the future, lists identified as deviating from the norm should not be used. The results of this study only partly agree with results from former studies.

[Prevalence of hearing impairment in northwestern Germany. Results of an epidemiological study on hearing status (HÖRSTAT)]. / Prävalenz von Schwerhörigkeit im Nordwesten Deutschlands : Ergebnisse einer epidemiologischen Untersuchung zum Hörstatus (HÖRSTAT).

BACKGROUND: A pure-tone average of 0.5, 1, 2, and 4 kHz in the better ear (PTA-4) is the international standard criterion set by the World Health Organization (WHO) to describe hearing loss. Presently, there are no epidemiological data on hearing loss in Germany based on this criterion. METHODS: A representative sample of adults from Oldenburg and Emden were invited for a hearing assessment. This article analyzes the association between hearing loss and age, sex, noise, occupation, and educational level. Age- and sex-specific prevalence rates following the WHO classification are compared with international findings. RESULTS: According to the WHO classification, the prevalence of hearing impairment in the study cohort (n=1,866) is approx. 16%. In men, who more commonly work in noisy jobs, a higher prevalence rate is observed than in women of the same age. Nevertheless, sex differences in the present study are smaller than those reported in most international studies. PTA-4 is approximately the same for men and women when effects of occupational noise are controlled, but differences in prevalence between occupational areas are still significant. CONCLUSION: Compared with international findings, age-specific prevalence rates in HÖRSTAT are low. In the synopsis of epidemiological studies of the past 25 years, a trend toward decreasing prevalence in middle and higher age groups can be observed.

[Traffic medicine expert opinions in otorhinolaryngology: current aspects]. / Verkehrsmedizinische Begutachtung in der HNO-Heilkunde : Aktuelle Aspekte.

According to German law granting of driving licenses depends on the proof of an adequate driving capability. The corresponding guidelines are at present in the process of being revised. At the moment bilateral deafness and high-grade hearing loss (> or = 60% in pure tone audiometry) are not exclusion criteria for driving licenses grades A, B and C, while driving licenses grade D and licenses for public transport are generally excluded. In the forthcoming revised edition of the guidelines it has been suggested that the latter group will also not be excluded. The regulations concerning dizziness are wide-sweeping at the moment as no driving license will be granted if dizziness is present but will be more specific in the next issue. In particular a division will be made between single axle and two axle vehicles. An expert assessment about driving suitability can only be made by a certified specialist with qualifications in traffic medicine.

Auditory filter bandwidths in binaural and monaural listening conditions.

The shape and the effective bandwidth of the auditory filter at 500 Hz was examined for binaural and monaural tone-in-noise detection experiments in four normal listeners. In the binaural condition, a broadband noise with an interaural phase difference of 0 below and an interaural phase difference of pi above a certain "edge frequency" was employed to mask a 500-Hz probe tone with an interaural phase pi (denoted as No pi S pi). The threshold of the probe tone as a function of the edge frequency in this configuration and in a configuration with an inverted interaural phase of the masker (denoted as N pi oS pi) was fitted by assuming different filter shapes and optimizing their respective parameters. In an analogous monaural experiment, the spectral power density of the masker was 15 dB lower below the "edge frequency" or 15 dB lower above this frequency, respectively. Several filter characteristics with two free parameters describe the data almost equally well. Their equivalent rectangular bandwidths (ERB) show considerably more variations between filter shapes than the 10-dB bandwidth and the 90% bandwidth values (i.e., the bandwidths encompassing 90% of the integrated area above and below the center frequency). This indicates that either of these two bandwidth parameters is more appropriate for comparing auditory filter bandwidths than the ERB. For the rounded exponential filter, the 90% bandwidth averages to 147 Hz in the binaural and to 125 Hz in the monaural condition. These values are up to 12% higher if off-frequency detection is accounted for. Our general finding of auditory filter bandwidths in the binaural conditions exceeding the monaural bandwidths by approximately 20% may be caused by two factors: First, off-frequency detection may be performed in monaural, but not in binaural detections tasks and second, the random interaural mismatch in binaural noise reduction processes fluctuates slowly and thus modulates and spectrally smears the output signal of the binaural noise reduction process.

Speech intelligibility prediction in hearing-impaired listeners based on a psychoacoustically motivated perception model.

Sensorneural hearing-impaired listeners suffer severely from deterioration in the processing and internal representation of acoustic signals. In order to understand this deterioration in detail, a numerical perception model was developed which is based on current functional models of the signal processing in the auditory system. To test this model, the individual's speech intelligibility in quiet and in noise was predicted. The primary input parameter of the model is the precisely measured audiogram of each listener. In a refined version of the model, additional input parameters are derived from predicting the individual's temporal forward masking and notched-noise measurements with the same model assumptions. The predictions of the perception model were compared with those of the articulation index (AI) and the speech transmission index (STI). The accuracy of prediction with the perception model is in the same range as with the AI and the STI. The model does not require a calibration function and has the advantage of a greater flexibility in including different processing deficits associated with hearing impairment. However, it requires more time for computation. For the hearing-impaired listeners examined so far the individually measured psychoacoustical parameters have only a secondary effect on the prediction as compared to the audiogram. Nevertheless, the underlying model is a first step toward a quantitative understanding of speech intelligibility and helps to distinguish between the influence of the "attenuation" and the "distortion" component of the hearing loss.

Binaural and monaural auditory filter bandwidths and time constants in probe tone detection experiments.

Auditory filter bandwidths and time constants were obtained with five normal-hearing subjects for different masker configurations both in the frequency and time domain for monaural and binaural listening conditions. Specifically, the masking level in the monaural condition and the interaural correlation in the binaural conditions, respectively, was changed in a sinusoidal, stepwise, and rectangular way in the frequency domain. In the corresponding experiments in the time domain, a sinusoidal and stepwise change of the masker was performed. From these results, a comparison was made across conditions to evaluate the influence of the factors "shape of transition," "monaural versus binaural," "frequency domain versus time domain," and "subject." Also, the respective data from the literature were considered using the same model assumptions and fitting strategy as used for the current data. The results indicate that the monaural auditory filter bandwidths and time constants fitted to the data are consistent across conditions both for the data included in this study and the data from the literature. No consistent relation between individual auditory filter bandwidths and time constants were found across subjects. For the binaural conditions, however, considerable differences were found in estimates of the bandwidths and time constants, respectively, across conditions. The reason for this mismatch seems to be the different detection strategies employed for the various tasks that are affected by the consistency of binaural information across frequency and time. While monaural detection performance appears to be modeled quite well with a linear filter or temporal integration window, this does not hold for the binaural conditions where both larger bandwidth and time constant estimates are found.

Effects of phase and level on vowel identification: data and predictions based on a nonlinear basilar-membrane model.

This paper examines the role of component phase and level on vowel identification and interprets the results in terms of the shapes of the waveforms occurring at the outputs of the filters in a nonlinear basilar-membrane model. Four normally hearing subjects were asked to identify which of six possible vowel-like harmonic complexes was presented on each trial. The stimuli were complex tones containing the first 35 harmonics of a 100-Hz fundamental. All of the harmonics below 3000 Hz were equal in amplitude except for three pairs of successive harmonics, at frequencies corresponding to the first three formants of six vowels, which were incremented in level relative to the background harmonics by 1, 2, 4, 8, and 16 dB. The components in the harmonic complexes were added in four different starting phase relationships; cosine, random, Schroeder positive, and Schroeder negative. The stimuli were presented at three overall levels; 85, 65, and 45 dB SPL. Performance was similar for the random and Schroeder-negative phases and did not vary as a function of level. Performance for the cosine- and Schroeder-positive-phase conditions was better than for the other two phase conditions, but decreased as the level was reduced. Performance for all four phase conditions was equivalent for the lowest level. The variation in performance as a function of level and component phase is explained in terms of the shapes of the temporal waveforms that would occur at the output of nonlinear "basilar-membrane filters" [H. W. Strube, J. Acoust. Soc. Am. 79, 1511-1518 (1986)], with asymmetric phase responses about the center frequency.