Helia Relaño-Iborra

Vocoded speech is widely used to simulate aspects of cochlear implant listening, and modeling vocoded intelligibility in normal-hearing listeners can provide insight into auditory processing under electric hearing. Sentence recognition was measured using three masker types (speech-shaped noise, tone complex, and noise-modulated tone complex) and four processing conditions (unprocessed, bandpass-filtered, tone-vocoded, and tone-vocoded with simulated current spread). Masker type affected intelligibility in all conditions except vocoded speech with simulated current spread. A modified speech-based envelope power spectrum model with a correlation-based decision stage was fitted to the unprocessed speech-shaped-noise condition and then applied, without re-fitting, to the remaining conditions. The model captured masker-dependent intelligibility patterns for unprocessed, bandpass-filtered, and tone-vocoded speech without simulated current spread. Analyses of the model's internal representations suggested that vocoding-related intelligibility loss was driven mainly by the removal of higher-rate temporal-envelope modulations rather than by reduced spectral resolution. With simulated current spread, the model predicted the loss of benefit for unmodulated maskers but consistently overestimated intelligibility. These findings support the view that modulation masking is not the primary limitation in simulated electric hearing and point to envelope-energy and pitch-related distortions as important targets for future cochlear implant-oriented intelligibility models.

Spectro-temporal modulation (STM) sensitivity has been proposed as a sensitive marker of speech intelligibility in challenging listening conditions, yet the underlying auditory mechanisms involved in STM detection remain incompletely understood. The present study measured STM detection thresholds in young normal-hearing and older hearing-impaired listeners and evaluated whether the revised Computational Auditory Signal Processing and Perception model (CASP) can account for individual performance. Thresholds were obtained for six modulation detection conditions, defined by combinations of spectral (0, 1, and 2 c/o) and temporal (4 and 12 Hz) rates. To individualize CASP, outer and inner hair cell loss estimates were obtained from audiometric and Adaptive Categorical Loudness Scaling (ACALOS) data. The results showed systematically elevated thresholds in older hearing-impaired listeners as compared to the young normal-hearing group, particularly at higher spectral rates. The model simulations reproduced overall threshold patterns, but substantially underestimated group differences and interindividual variability in the data. Moreover, the simulations showed limited sensitivity to estimates of outer and inner hair cell loss, supporting the idea that additional supra-threshold mechanisms contribute to STM deficits. While these findings demonstrate the potential of auditory models to predict STM performance, they also highlight the need for refined representations of peripheral and central processing to account for individual STM detection thresholds.

Spectro-temporal modulation (STM) sensitivity has been proposed as a sensitive marker of speech intelligibility in challenging listening conditions, yet the underlying auditory mechanisms involved in STM detection remain incompletely understood. The present study measured STM detection thresholds in young normal-hearing and older hearing-impaired listeners and evaluated whether the revised Computational Auditory Signal Processing and Perception model [CASP, Paulick et al . (2025). J.Acoust.Am. 157 (5), 3232–3244] can account for individual performance. Thresholds were obtained for six modulation detection conditions, defined by combinations of spectral (0, 1, 2 c/o) and temporal (4, 12 Hz) rates. To individualise CASP, outer and inner hair cell loss estimates were obtained from audiometric and Adaptive Categorical Loudness Scaling (ACALOS) data. The results showed systematically elevated thresholds in older hearing-impaired listeners as compared to the young normal-hearing group, particularly at higher spectral rates. The model simulations reproduced overall threshold patterns, but substantially underestimated group differences and inter-individual variability in the data. Moreover, the simulations showed limited sensitivity to estimates of outer and inner hair cell loss, supporting the idea that additional supra-threshold mechanisms contribute to STM deficits. While these findings demonstrate the potential of auditory models to predict STM performance, they also highlighting the need for refined representations of peripheral and central processing to account for individual STM detection thresholds.

This study integrates a non-linear inner hair cell model (IHC) into the computational auditory signal processing and perception (CASP) model [Jepsen, Ewert, and Dau (2008). J. Acoust. Am. 124(1), 422–438]. The integration addresses limitations of its more simplistic predecessor that did not reflect the saturation of the IHC transduction process towards high sound pressure levels. While exhibiting distinct processing mechanisms compared to the original model, the revised model maintains predictive power across conditions of intensity discrimination, simultaneous and forward masking, and modulation detection, effectively accounting for data from normal-hearing listeners. Additional updates and refinements to the model are introduced in response to the changes produced by the additional compressive non-linearity and to improve its usability. Overall, the revised CASP model offers a more accurate and intuitive framework for simulating auditory processing and perception under diverse conditions and tasks. This enhanced version may be particularly valuable for studying the influence of the ear's nonlinear response properties on internal auditory representations, including the effects of sensorineural hearing loss on auditory perception.

The perception of amplitude modulation (AM), characterized by a frequency-selective process in the modulation domain, is considered critical for speech intelligibility. Previous literature has provided evidence of an age-related decline in AM frequency selectivity. Additionally, a notable sharpening of AM tuning with hearing loss has been observed, which was proposed to be related to a perceptual advantage resulting from peripheral compression loss. This study explores whether such changes in AM tuning with age and hearing loss contribute to the speech intelligibility challenges older listeners often face in noisy environments. Young (n = 10, aged 22–28 years) and older (n = 9, aged 57–77 years) listeners with normal hearing as well as older listeners with hearing impairment (n = 9, aged 64–77 years) participated in the study. All had previously taken part in studies on AM tuning. Speech-reception thresholds (SRTs) were collected under conditions including stationary, fluctuating, and competing-speech maskers. The results revealed an age-related increase in SRTs, with an additional negative impact of hearing loss. Beyond age and audibility, a measure of AM tuning significantly contributed to explaining the variance in SRTs across listeners for specific maskers. These findings motivate further exploration of the relationship between AM frequency selectivity and speech intelligibility in noise.

The processing and perception of amplitude modulation (AM) in the auditory system reflect a frequency-selective process, often described as a modulation filterbank. Previous studies on perceptual AM masking reported similar results for older listeners with hearing impairment (HI listeners) and young listeners with normal hearing (NH listeners), suggesting no effects of age or hearing loss on AM frequency selectivity. However, recent evidence has shown that age, independently of hearing loss, adversely affects AM frequency selectivity. Hence, this study aimed to disentangle the effects of hearing loss and age. A simultaneous AM masking paradigm was employed, using a sinusoidal carrier at 2.8 kHz, narrowband noise modulation maskers, and target modulation frequencies of 4, 16, 64, and 128 Hz. The results obtained from young (n = 3, 24–30 years of age) and older (n = 10, 63–77 years of age) HI listeners were compared to previously obtained data from young and older NH listeners. Notably, the HI listeners generally exhibited lower (unmasked) AM detection thresholds and greater AM frequency selectivity than their NH counterparts in both age groups. Overall, the results suggest that age negatively affects AM frequency selectivity for both NH and HI listeners, whereas hearing loss improves AM detection and AM selectivity, likely due to the loss of peripheral compression.

The perception of amplitude modulation (AM), characterized by a frequency-selective process in the modulation domain, is considered critical for speech intelligibility. Previous literature has provided evidence of an age-related decline in AM frequency selectivity. Additionally, a notable sharpening of AM tuning with hearing loss has been observed, which was proposed to be related to a perceptual advantage resulting from peripheral compression loss. This study explores whether such changes in AM tuning with age and hearing loss contribute to the speech intelligibility challenges that older listeners often face in noisy environments. Young (n=10, 22-28 years) and older (n=9, 57-77 years) listeners with normal hearing as well as older listeners with hearing impairment (n=9, 64-77 years) participated in the study. All had previously taken part in studies on AM tuning. Speech-reception thresholds (SRTs) were collected in conditions including stationary, fluctuating, and competing-speech maskers. The results revealed an age-related increase in SRTs, with an additional negative impact of hearing loss. Beyond age and audibility, a measure of AM tuning significantly contributed to explaining the variance in SRTs across listeners for specific maskers. These findings motivate further exploration of the relationship between AM frequency selectivity and speech intelligibility in noise.

The processing and perception of amplitude modulation (AM) in the auditory system reflect a frequency-selective process, often described as a modulation filterbank. Previous studies on perceptual AM masking reported similar results for older listeners with hearing impairment (HI) and young listeners with normal hearing (NH), suggesting no effects of age or hearing loss on AM frequency selectivity. However, recent evidence has shown that age, independently of hearing loss, adversely affects AM frequency selectivity. Hence, this study aimed to disentangle the effects of hearing loss and age. A simultaneous AM masking paradigm was employed, utilizing a sinusoidal carrier at 2.8 kHz, narrow-band noise modulation maskers, and target modulation frequencies of 4, 16, 64, and 128 Hz. The results obtained from young (n=3, 24-30 years) and older (n=10, 63-77 years) HI listeners were compared to previously obtained data from young and older NH listeners. Notably, the HI listeners generally exhibited lower (unmasked) AM detection thresholds and greater AM frequency selectivity than their NH counterparts in both age groups. Overall, the results suggest that age negatively affects AM frequency selectivity for both NH and HI listeners, while hearing loss improves AM detection and AM selectivity, likely due to the loss of peripheral compression.

Purpose: The average fundamental frequency separation (∆ f _o ) between two competing voices has been shown to provide an important cue for target-speech intelligibility. However, some of the previous investigations used speech materials with linguistic properties and f _o characteristics that may not be typical of realistic acoustic scenarios. This study investigated to what extent the effect of ∆ f _o generalizes to more real-life speech. Methods: Real-life sentences and a well-controlled method for manipulating the acoustic stimuli were employed. Fifteen young normal-hearing native Danish listeners were tested in a two-competing-voices sentence recognition task at several target-to-masker ratios (TMRs) and ∆ f _o s . Results: Compared to previous studies that addressed the same experimental scenario with less realistic speech materials, the present results showed only a moderate effect of ∆ f _o at negative TMRs and a negligible effect at positive TMRs. An analysis of the employed stimuli showed that a large ∆ f _o effect on the target speech intelligibility is only observed when the competing sentences have highly synchronous f _o trajectories, which is typical of the artificial speech materials employed in previous studies. Conclusion: Overall, the present results suggest a relatively small effect of ∆ f _o on the intelligibility of real-life speech, as compared to previously employed artificial speech, in two-competing-sentences conditions.

The perception of amplitude modulations (AMs) has been characterized by a frequency-selective process in the temporal envelope domain and simulated in computational auditory processing and perception models using a modulation filterbank. Such AM frequency-selective processing has been argued to be critical for the perception of complex sounds, including speech. This study aimed at investigating the effects of age on behavioral AM frequency selectivity in young (n = 11, 22–29 years) versus older (n = 10, 57–77 years) listeners with normal hearing, using a simultaneous AM masking paradigm with a sinusoidal carrier (2.8 kHz), target modulation frequencies of 4, 16, 64, and 128 Hz, and narrowband-noise modulation maskers. A reduction of AM frequency selectivity by a factor of up to 2 was found in the older listeners. While the observed AM selectivity co-varied with the unmasked AM detection sensitivity, the age-related broadening of the masked threshold patterns remained stable even when AM sensitivity was similar across groups for an extended stimulus duration. The results from the present study might provide a valuable basis for further investigations exploring the effects of age and reduced AM frequency selectivity on complex sound perception as well as the interaction of age and hearing impairment on AM processing and perception.