Publications Search Results
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PublicationRelation between hearing abilities and preferred playback settings for speech perception in complex listening conditions( 2021)
;Kubiak, Aleksandra M. ;Rennies, Jan ;Ewert, Stephan D.Objective This study investigated if individual preferences with respect to the trade-off between a good signal-to-noise ratio and a distortion-free speech target were stable across different masking conditions and if simple adjustment methods could be used to identify subjects as either ""noise haters"" or ""distortions haters"". Design In each masking condition, subjects could adjust the target speech level according to their preferences by employing (i) linear gain or gain at the cost of (ii) clipping distortions or (iii) compression distortions. The comparison of these processing conditions allowed investigating the preferred trade-off between distortions and noise disturbance. Study sample Thirty subjects differing widely in hearing status (normal-hearing to moderately impaired) and age (23-85 years). Results High test-retest stability of individual preferences was found for all modification schemes. The preference adjustments suggested that subjects could be consistently categorised along a scale from ""noise haters"" to ""distortion haters"", and this preference trait remained stable through all maskers, spatial conditions, and types of distortions. Conclusions Employing quick self-adjustment to collect listening preferences in complex listening conditions revealed a stable preference trait along the ""noise vs. distortions"" tolerance dimension. This could potentially help in fitting modern hearing aid algorithms to the individual user.
PublicationPrediction of individual speech recognition performance in complex listening conditions( 2020)
;Kubiak, Aleksandra M. ;Rennies, Jan ;Ewert, Stephan D.This study examined how well individual speech recognition thresholds in complex listening scenarios could be predicted by a current binaural speech intelligibility model. Model predictions were compared with experimental data measured for seven normal-hearing and 23 hearing-impaired listeners who differed widely in their degree of hearing loss, age, as well as performance in clinical speech tests. The experimental conditions included two masker types (multi-talker or two-talker maskers), and two spatial conditions (maskers co-located with the frontal target or symmetrically separated from the target). The results showed that interindividual variability could not be well predicted by a model including only individual audiograms. Predictions improved when an additional individual ""proficiency factor"" was derived from one of the experimental conditions or a standard speech test. Overall, the current model can predict individual performance relatively well (except in conditions high in informational masking), but the inclusion of age-related factors may lead to even further improvements.
PublicationRestoring perceived loudness for listeners with hearing loss( 2018)
;Oetting, Dirk ;Hohmann, Volker ;Appell, Jens-E. ;Ewert, Stephan D.Objectives: Normalizing perceived loudness is an important rationale for gain adjustments in hearing aids. It has been demonstrated that gains required for restoring normal loudness perception for monaural narrowband signals can lead to higher-than-normal loudness in listeners with hearing loss, particularly for binaural broadband presentation. The present study presents a binaural bandwidth-adaptive dynamic compressor (BBDC) that can apply different gains for narrow- and broadband signals. It was hypothesized that normal perceived loudness for a broad variety of signals could be restored for listeners with mild to moderate high-frequency hearing loss by applying individual signal-dependent gain corrections. Design: Gains to normalize perceived loudness for narrowband stimuli were assessed in 15 listeners with mild to moderate high-frequency hearing loss using categorical loudness scaling. Gains for narrowband loudness compensation were calculated and applied in a standard compressor. Aided loudness functions for signals with different bandwidths were assessed. The deviation from the average normal-hearing loudness functions was used for gain correction in the BBDC. Aided loudness functions for narrow- and broadband signals with BBDC were then assessed. Gains for a 65 dB SPL speech-shaped noise of BBDC were compared with gains based on National Acoustic Laboratories' nonlinear fitting procedure version 2 (NAL-NL2). The perceived loudness for 20 real signals was compared to the average normal-hearing rating. Results: The suggested BBDC showed close-to-normal loudness functions for binaural narrow- and broadband signals for the listeners with hearing loss. Normal loudness ratings were observed for the real-world test signals. The proposed gain reduction method resulted on average in similar gains as prescribed by NAL-NL2. However, substantial gain variations compared to NAL-NL2 were observed in the data for individual listeners. Gain corrections after narrowband loudness compensation showed large interindividual differences for binaural broadband signals. Some listeners required no further gain reduction for broadband signals; for others, gains in decibels were more than halved for binaural broadband signals. Conclusion: The interindividual differences of the binaural broadband gain corrections indicate that relevant information for normalizing perceived loudness of binaural broadband signals cannot be inferred from monaural narrowband loudness functions. Over-amplification can be avoided if binaural broadband measurements are included in the fitting procedure. For listeners with a high binaural broadband gain correction factor, loudness compensation for narrowband and broadband stimuli cannot be achieved by compression algorithms that disregard the bandwidth of the input signals. The suggested BBDC includes individual binaural broadband corrections in a more appropriate way than threshold-based procedures.
PublicationCharacterizing individual hearing loss using narrow-band loudness compensation( 2016)
;Oetting, Dirk ;Appell, Jens-E. ;Hohmann, VolkerEwert, Stephan D.Loudness is one of the key factors related to overall satisfaction with hearing aids. Individual loudness functions can reliably be measured using categorical loudness scaling (CLS) without any training. Nevertheless, the use of loudness measurement like CLS is by far less common than use of audiometric thresholds to fit hearing aids, although loudness complaints are one of the most mentioned reasons for revisiting the hearing aid dispenser. A possible reason is that loudness measurements are typically conducted with monaural narrow-band signals while binaural broad-band signals as speech or environmental sounds are typical in daily life. This study investigated individual uncomfortable loudness levels (UCL) with a focus on monaural and binaural broad-band signals, as being more realistic compared to monaural narrow-band signals. Nine normal-hearing listeners served as a reference in this experiment. Six hearing-impaired listeners with similar audiograms were aided with a simulated hearing aid, adjusted to compensate the narrow-band loudness perception back to normal. As desired, monaural narrow-band UCLs were restored to normal, however large individual deviations of more than 30 dB were found for the binaural broad-band signal. Results suggest that broad-band and binaural loudness measurements add key information about the individual hearing loss beyond the audiogram.
PublicationSpectral and binaural loudness summation for hearing-impaired listeners( 2016)
;Oetting, Dirk ;Hohmann, Volker ;Appell, Jens-E. ;Ewert, Stephan D.Sensorineural hearing loss typically results in a steepened loudness function and a reduced dynamic range from elevated thresholds to uncomfortably loud levels for narrowband and broadband signals. Restoring narrowband loudness perception for hearing-impaired (HI) listeners can lead to overly loud perception of broadband signals and it is unclear how binaural presentation affects loudness perception in this case. Here, loudness perception quantified by categorical loudness scaling for nine normal-hearing (NH) and ten HI listeners was compared for signals with different bandwidth and different spectral shape in monaural and in binaural conditions. For the HI listeners, frequency- and level-dependent amplification was used to match the narrowband monaural loudness functions of the NH listeners. The average loudness functions for NH and HI listeners showed good agreement for monaural broadband signals. However, HI listeners showed substantially greater loudness for binaural broadband signals than NH listeners: on average a 14.1 dB lower level was required to reach ""very loud"" (range 30.8 to −3.7 dB). Overall, with narrowband loudness compensation, a given binaural loudness for broadband signals above ""medium loud"" was reached at systematically lower levels for HI than for NH listeners. Such increased binaural loudness summation was not found for loudness categories below ""medium loud"" or for narrowband signals. Large individual variations in the increased loudness summation were observed and could not be explained by the audiogram or the narrowband loudness functions.
PublicationIndividualisierte Vorhersage von Lautheit bei Schwerhörenden( 2016)
;Pieper, Iko ;Mauermann, Manfred ;Oetting, DirkEwert, Stephan D.Die Lautheitswahrnehmung verändert sich bei Hörschädigungen gegenüber der von Normalhörenden. Dies kann z.B. mit Hilfe der kategorialen Lautheitsskalierung (KLS) erfasst werden. Neben der frequenzabhängigen Anhebung der Ruhehörschwelle ist eine weitere typische Beobachtung der steilere Verlauf der Lautheitsfunktion bei Erhöhung des Pegels. Der individuelle Verlauf der Lautheitsfunktion kann durch bestehende Lautheitsmodelle häufig nur unzureichend beschrieben werden (e.g., Oetting et al. 2013). Hier wird ein physiologisch motiviertes Lautheitsmodell vorgestellt, das mögliche Ursachen dieser Beobachtungen eingrenzen soll: Dabei erlaubt die Verwendung eines nichtlinearen Transmission-Line Modells eine getrennte Betrachtung des Einflusses von äußeren und inneren Haarzellenverlust auf die Lautheit. Die individuellen Modellparameter wurden mit Hilfe des Audiogramms und der unteren Steigungen der schmalbändigen Lautheitsfunktion bestimmt. Der frequenzabhängige äußere Haarzellenverlust wird dafür mittels Reduzierung der ortsabhängigen und typischerweise nichtlinearen Verstärkung der im Transmission-Line Modell simulierten Basilarmembran-schwingungen realisiert. Der innere Haarzellenverlust wird als ortsabhängige lineare Abschwächung abgebildet. Zur Vorhersage individueller schmalbandiger Lautheitsfunktionen musste eine zusätzliche lineare ortsabhängige Verstärkung (central gain) angenommen werden, um auch bei hohen Pegeln eine gute individuelle Vorhersage der Lautheit zu erreichen. Die so angepassten Lautheitsmodelle sind mit Hilfe von Lautheitsfunktionen von breitbandigen Signalen evaluiert worden. Physiologisch realistische Modelle, die auf den individuellen Probanden angepasst werden können, sind wichtige Werkzeuge bei der Suche nach geeigneten diagnostischen Methoden zur besseren Differenzierung der genauen Ursachen von individuellen Hörverlusten.
PublicationDeriving sound quality measures from a perceptual modelThere is a growing need for objective measures that provide a reproducible and reliable characterization of sound quality in many practical areas of sound design engineering. In current practice and research, however, the commonly used measures are rather simple technical measures (e.g. weighted sound pressure levels) or psychoacoustic measures (e.g. loudness, sharpness, roughness). These measures need to be verified for every new class of signals, and usually a different and newly adapted combination of several metrics is required to predict more high-level percepts such as sound annoyance or preference. Another promising approach to develop more generally applicable models is to employ perceptual models that incorporate all of the basic mechanisms underlying human sound perception (hearing thresholds, limited temporal and spectral resolution, dynamic compression, etc.). In this study, the output of an existing perceptual model is used to derive measures for evaluating the perceived quality of different stimuli. This includes artificial stimuli from fundamental psychoacoustic experiments (e.g. roughness perception) as well as real product sounds from other sound quality studies. The results are compared to experimental data and existing quality measures in order to evaluate the potential of the psychophysical model as frontend for sound quality evaluation.
PublicationApplication of psychophysical models for audibility prediction of technical signals in real-world background noiseA valid, objective computation of whether a real-world sound is detectable in a real-world acoustical environment is highly desirable in many noise control applications. However, most current prediction approaches have not been validated for this purpose and have not been tailored towards predicting the influence of certain signal features, such as the temporal structure or the spectral content of the masker or target. In order to evaluate the applicability of prediction approaches with respect to these signal features, detection thresholds of various real-world signals were measured for normal-hearing listeners. The detection thresholds depended on the temporal structure and spectrum of the target and the spectrum of the masker. The data were compared to predictions of five approaches ranging from time-averaged technical measures to psychoacoustic models, which incorporate these signal features to different extents. In general, the correspondence between predictions and the experimental data was better for the psychoacoustic models than for the results of the technical measures. Even though all models could account for most of the key effects in the experimental data, only the psychoacoustic models were able to predict the influence of the temporal structure of the signals. One of the models showed clear advantages in prediction performance, reaching an overall determination coefficient of R-2 = 0.94. This underlines the applicability of psychoacoustic models for correctly predicting audibility in real-world applications.
PublicationOptimized loudness-function estimation for categorical loudness scaling data( 2014)
;Oetting, Dirk ;Brand, ThomasEwert, Stephan D.Individual loudness perception can be assessed using categorical loudness scaling (CLS). The procedure does not require any training and is frequently used in clinics. The goal of this study was to investigate different methods of loudness-function estimation from CLS data in terms of their test-retest behaviour and to suggest an improved method compared to Brand and Hohmann (2002) for adaptive CLS. Four different runs of the CLS procedure were conducted using 13 normal-hearing and 11 hearing-impaired listeners. The following approaches for loudness-function estimation (fitting) by minimising the error between the data and loudness function were compared: Errors were defined both in level and in loudness direction, respectively. The hearing threshold level (HTL) was extracted from CLS by splitting the responses into an audible and an inaudible category. The extracted HTL was used as a fixed starting point of the loudness function. The uncomfortable loudness level (UCL) was estimated if presentation levels were not sufficiently high to yield responses in the upper loudness range, as often observed in practise. Compared to the original fitting method, the modified estimation of the HTL was closer to the pure-tone audiometric threshold. Results of a computer simulation for UCL estimation showed that the estimation error was reduced for data sets with sparse or absent responses in the upper loudness range. Overall, the suggested modifications lead to a better test-retest behaviour. If CLS data are highly consistent over the whole loudness range, all fitting methods lead to almost equal loudness functions. A considerable advantage of the suggested fitting method is observed for data sets where the responses either show high standard deviations or where responses are not present in the upper loudness range. Both cases regularly occur in clinical practice.
PublicationApplication of psychoacoustic models for predicting detection thresholds of real signals in real backgrounds( 2014)
;Schell-Majoor, Lena ;Rennies, Jan ;Ewert, Stephan D.