Spectrotemporal Modulation Sensitivity Research Articles

The Audible Contrast Threshold (ACT) test: A clinical spectro-temporal modulation detection test

Over the last decade, multiple studies have shown that hearing-impaired listeners’ speech-in-noise reception ability, measured with audibility compensation, is closely associated with performance in spectro-temporal modulation (STM) detection tests. STM tests thus have the potential to provide highly relevant beyond-the-audiogram information in the clinic, but the available STM tests have not been optimized for clinical use in terms of test duration, required equipment, and procedural standardization. The present study introduces a quick-and-simple clinically viable STM test, named the Audible Contrast Threshold (ACT™) test. First, an experimenter-controlled STM measurement paradigm was developed, in which the patient is presented bilaterally with a continuous audibility-corrected noise via headphones and asked to press a pushbutton whenever they hear an STM target sound in the noise. The patient's threshold is established using a Hughson-Westlake tracking procedure with a three-out-of-five criterion and then refined by post-processing the collected data using a logistic function. Different stimulation paradigms were tested in 28 hearing-impaired participants and compared to data previously measured in the same participants with an established STM test paradigm. The best stimulation paradigm showed excellent test-retest reliability and good agreement with the established laboratory version. Second, the best stimulation paradigm with 1-second noise “waves” (windowed noise) was chosen, further optimized with respect to step size and logistic-function fitting, and tested in a population of 25 young normal-hearing participants using various types of transducers to obtain normative data. Based on these normative data, the “normalized Contrast Level” (in dB nCL) scale was defined, where 0 ± 4 dB nCL corresponds to normal performance and elevated dB nCL values indicate the degree of audible contrast loss. Overall, the results of the present study suggest that the ACT test may be considered a reliable, quick-and-simple (and thus clinically viable) test of STM sensitivity. The ACT can be measured directly after the audiogram using the same set up, adding only a few minutes to the process.

Comparison of spectral resolution and spectro-temporal modulation sensitivity well above and near the hearing threshold

Spectral resolution and spectro-temporal modulation (STM) sensitivity both show a correlation with speech reception thresholds in noise. Both are also sensitive to the difficulties resulting from sensorineural hearing loss; however, the relationship between the two is not fully understood. The present study investigated the potential relationship between spectral resolution and STM sensitivity and the impact of presentation level in young, normal hearing listeners. Four noise carriers were tested with the two broader bandwidths and two 1-octave wide bandwidths: 200–6400 Hz, 1250–5000 Hz, 1250–2500 Hz, & 2500–5000 Hz. Presentation levels were 70 dB SPL and 20 dB SL relative to the individual’s pure-tone frequency-shaped noise carrier threshold. Spectral resolution was tested using a phase reversal paradigm, also known as a spectral ripple discrimination task, with thresholds measured in cycles per octave. Spectral, temporal, and STM sensitivity were each tested using a depth detection task, with thresholds measured in dB. On a test-by-test case, results were aligned with past studies that included a single test. The results show that both sensitivities are distinct at a low presentation level close to individual hearing thresholds, and a mixed relationship between both measures indicate that spectral resolution may only be one contributor to STM sensitivity.

Psychophysical performance differences associated with auditory spatial attention in older listeners with and without hearing loss

In a busy listening environment with multiple speakers, even normal-hearing listeners may face difficulties in understanding speech (i.e., “the cocktail party problem”). Individual factors related to bottom-up and/or top-down processing difficulties may be associated with the listener’s ability to attend to speech, a key component in navigating complex acoustic environments. The present study tested listeners on a battery of psychophysical measures and compared listener performance to cortical measures (EEG) of spatial-change tuning and auditory spatial attention. The behavioral tests measured both perceptual and cognitive performance and included: frequency modulation detection, spectro-temporal modulation sensitivity, spatial release from masking, temporal gap detection, auditory and non-auditorysustained attention, and visuo-spatial problem solving. The EEG paradigm tested the listener’s ability to attend to moving speech in quiet or background babble in the free field. Older listeners with and without hearing loss (n = 20 per group) demonstrated wide individual performance for some measures and significant correlations between behavioral thresholds and cortical responses, consistent with a more refined view of age-related hearing loss and a need for a more holistic approach in diagnoses for individuals beyond standard clinical tests. [Work supported by NIH R21DC017832.]

Comparison of hearing aid fitting effectiveness with audiograms from either user-operated or traditional audiometry in a clinical setting: a study protocol for a blinded non-inferiority randomised controlled trial

IntroductionThere is a worldwide need to enhance the capacity of audiometry testing. The objective of this study is to compare the User-operated Audiometry (UAud) system with traditional audiometry in a...

Aging effects on binaural listening and other auditory system assessments

Older listeners are known to have decreased sound localization and hearing in noise abilities compared to young listeners, even when exhibiting clinically normal hearing. We hypothesize that these deficits may be related to decreased temporal precision of neural activity in the sound localization processing pathway, and/or other central auditory system deficits involving more complex functions such as speech recognition. Presented here are preliminary results from a study underway on the impact of aging on auditory functioning, and in particular, binaural processing. Subjects range from 21 to 89 years of age, have normal or near normal-hearing sensitivity, and are being evaluated on assessments of auditory system integrity and behavioral performance. Primary outcome measures include speech understanding in noise, auditory brainstem responses (ABRs) and the calculated ABR binaural interaction component, behavioral measures of spatial acuity, and a subjective questionnaire of hearing handicap. Secondary measures include temporal fine structure and spectro-temporal modulation sensitivity tests, otoacoustic emissions, and electrocochleography. In addition, extended-high-frequency hearing thresholds are measured and working memory assessed. Early results show an aging effect across decades of life on several of these measures. Greatest aging effects are seen in the more adverse listening conditions from behavioral testing. [Support: R01-DC017924.]

Contributed Session I: Effects of Aging on Speech-in-Noise Discrimination

The ability to discriminate speech in the presence of background noise decreases with age. The current study examined the effects of noise type and spatial separation between the target and masking speech on speech-in-noise (SiN) discrimination in older (22) and young (25) adults. Using Portable Automated Rapid Testing software implemented on an iPad, participants were asked to separate target speech from either interfering speech (informational masking) or 'garbled speech' that contained similar spectro-temporal aspects of sound, but no informational meaning (energetic masking) for three spatial separations (0°, 6°, and 45°). In addition, spectro-temporal modulation (STM) sensitivity, binaural sensitivity, and notched-noise masking thresholds were measured. Overall, older adults showed worse SiN performance compared to young controls for both types of masking at most of the spatial separations. In contrast to their worse sensitivity for binaural detection and notched-noise masking, older adults showed intact STM sensitivity. These findings add knowledge of how aging affects SiN discrimination and provide insight into training programs aimed at improving older adults' SiN performance.

Auditory Tests for Characterizing Hearing Deficits in Listeners With Various Hearing Abilities: The BEAR Test Battery.

The Better hEAring Rehabilitation (BEAR) project aims to provide a new clinical profiling tool—a test battery—for hearing loss characterization. Although the loss of sensitivity can be efficiently measured using pure-tone audiometry, the assessment of supra-threshold hearing deficits remains a challenge. In contrast to the classical “attenuation-distortion” model, the proposed BEAR approach is based on the hypothesis that the hearing abilities of a given listener can be characterized along two dimensions, reflecting independent types of perceptual deficits (distortions). A data-driven approach provided evidence for the existence of different auditory profiles with different degrees of distortions. Ten tests were included in a test battery, based on their clinical feasibility, time efficiency, and related evidence from the literature. The tests were divided into six categories: audibility, speech perception, binaural processing abilities, loudness perception, spectro-temporal modulation sensitivity, and spectro-temporal resolution. Seventy-five listeners with symmetric, mild-to-severe sensorineural hearing loss were selected from a clinical population. The analysis of the results showed interrelations among outcomes related to high-frequency processing and outcome measures related to low-frequency processing abilities. The results showed the ability of the tests to reveal differences among individuals and their potential use in clinical settings.

Normative psychoacoustic data using portable automated rapid testing (PART) iPad application

Psychoacoustic tasks have been used to evaluate auditory processing capabilities throughout many decades. Here, we present data for Spatial Release from Masking (SRM), gap detection thresholds (GDTs), and spectrotemporal modulation (STM) sensitivity on a large group of listeners varying in age and hearing acuity collected using the PART iPad application (https://braingamecenter.ucr.edu/games/p-a-r-t/). Coordinate Response Measure (CRM) sentences were used to quantify SRM. A 4 Hz-2 c/o spectrotemporally modulated broadband noise was used to quantify STM sensitivity. Broadband Gaussian noise was used to measure gap detection thresholds. Initial analyses revealed similar thresholds between traditional methods found in the literature and data collected through the PART application for all psychoacoustic tasks. The ease with which the data is collected using PART application is expected to aid clinicians in rapidly characterizing difficulties perceived by individuals in everyday listening scenarios and in evaluating patient progress with hearing aid adjustments and aural rehabilitation over time.

Spectro-temporal modulation detection and its relation to speech perception in children with auditory processing disorder

ObjectivesPoor speech perception in noise is one of the most common complaints reported for children with auditory processing disorder (APD). APD is defined as a deficit in perceptual processing of acoustic information in the auditory system in which decreased spectro-temporal resolution may also contribute. Since the recognition of spoken message in the context of other sounds, is based on the processing of auditory spectro-temporal modulations, the assessment of spectro-temporal modulations sensitivity can evaluate the listener's ability to retrieve and integrate speech segments covered by noise. Therefore, the purpose of this study was to examine spectro-temporal modulation (STM) detection and its relation to speech perception in children with APD and to compare the results with aged-matched normally developed children. Methods35 children with APD and 32 normal hearing children (8–12 years old) were enrolled. In order to examine STM detection performance, six different STM stimulus conditions were employed using three different temporal modulation rates (4, 12 and 32 Hz) and two different spectral modulation densities (0.5 and 2.0 cycles/octave). Initially, the STM detection thresholds at these six STM stimulus conditions were measured in both groups and the results were compared. Thereafter, the relation between STM detection thresholds and speech perception tests, including consonant-vowel in noise and word in noise tests were assessed. ResultsThe STM sensitivity was poorer than normal for APD children at all STM stimulus conditions. Children with APD displayed significantly poorer STM detection thresholds than those of normally developed children (p < 0.05). Significant correlations were found between STM detection thresholds and speech perception in noise in both groups (p < 0.05). ConclusionThe results suggest that the altered encoding of spectro-temporal acoustic cues in the auditory nervous system may be one of the underlying factors of reduced STM detection performance in children with APD. The present study may suggest that poor ability to extract STM cues in children with APD, can be an underlying factor for their listening problems in noise and poor speech perception in challenging situations.

Spectrotemporal Modulation Sensitivity in Cochlear-Implant and Normal-Hearing Listeners: Is the Performance Driven by Temporal or Spectral Modulation Sensitivity?

This study examined the contribution of temporal and spectral modulation sensitivity to discrimination of stimuli modulated in both the time and frequency domains. The spectrotemporally modulated stimuli contained spectral ripples that shifted systematically across frequency over time at a repetition rate of 5 Hz. As the ripple density increased in the stimulus, modulation depth of the 5 Hz amplitude modulation (AM) reduced. Spectrotemporal modulation discrimination was compared with subjects’ ability to discriminate static spectral ripples and the ability to detect slow AM. The general pattern from both the cochlear implant (CI) and normal hearing groups showed that spectrotemporal modulation thresholds were correlated more strongly with AM detection than with static ripple discrimination. CI subjects’ spectrotemporal modulation thresholds were also highly correlated with speech recognition in noise, when partialing out static ripple discrimination, but the correlation was not significant when partialing out AM detection. The results indicated that temporal information was more heavily weighted in spectrotemporal modulation discrimination, and for CI subjects, it was AM sensitivity that drove the correlation between spectrotemporal modulation thresholds and speech recognition. The results suggest that for the rates tested here, temporal information processing may limit performance more than spectral information processing in both CI users and normal hearing listeners.

The effect of presentation level on spectrotemporal modulation detection

The understanding of speech in noise relies (at least partially) on spectrotemporal modulation sensitivity. This sensitivity can be measured by spectral ripple tests, which can be administered at different presentation levels. However, it is not known how presentation level affects spectrotemporal modulation thresholds. In this work, we present behavioral data for normal-hearing adults which show that at higher ripple densities (2 and 4 ripples/oct), increasing presentation level led to worse discrimination thresholds. Results of a computational model suggested that the higher thresholds could be explained by a worsening of the spectrotemporal representation in the auditory nerve due to broadening of cochlear filters and neural activity saturation. Our results demonstrate the importance of taking presentation level into account when administering spectrotemporal modulation detection tests.

Spectrotemporal modulation sensitivity as a predictor of speech intelligibility in noise for hearing-impaired listeners

The audiogram accounts for only a portion of the variance in speech-reception performance in noise for hearing-impaired listeners. The remaining variance is often attributed to a combination of suprathreshold auditory distortion and non-auditory factors such as cognitive processing. This talk describes a series of studies demonstrating that a suprathreshold measure of sensitivity to spectro-temporal modulation (STM) can account for individual differences in speech-reception scores that are not predicted by the audiogram. STM stimuli are spectrally rippled noises with spectral-peak frequencies that shift over time, akin to modulations in a speech signal. The results show that STM sensitivity correlates to speech-reception performance in noise; that the correlation is ascribed mainly to the low-frequency portion of the stimulus (<2 kHz); and that STM sensitivity can account for individual differences in speech-reception thresholds for hearing-impaired listeners properly fit with individualized frequency-dependent gain. Hearing loss has the largest impact on STM sensitivity for low temporal rates and low carrier frequencies, suggesting a reduced ability to use temporal fine-structure information to detect slow-moving spectral peaks. STM detection is a fast, simple test of suprathreshold auditory function that complements the high-frequency audiogram to account for a substantial proportion of individual variability in speech reception in noise.

Spectrotemporal Modulation Sensitivity as a Predictor of Speech-Reception Performance in Noise With Hearing Aids.

The audiogram predicts <30% of the variance in speech-reception thresholds (SRTs) for hearing-impaired (HI) listeners fitted with individualized frequency-dependent gain. The remaining variance could reflect suprathreshold distortion in the auditory pathways or nonauditory factors such as cognitive processing. The relationship between a measure of suprathreshold auditory function—spectrotemporal modulation (STM) sensitivity—and SRTs in noise was examined for 154 HI listeners fitted with individualized frequency-specific gain. SRTs were measured for 65-dB SPL sentences presented in speech-weighted noise or four-talker babble to an individually programmed master hearing aid, with the output of an ear-simulating coupler played through insert earphones. Modulation-depth detection thresholds were measured over headphones for STM (2cycles/octave density, 4-Hz rate) applied to an 85-dB SPL, 2-kHz lowpass-filtered pink-noise carrier. SRTs were correlated with both the high-frequency (2–6 kHz) pure-tone average (HFA; R2 = .31) and STM sensitivity (R2 = .28). Combined with the HFA, STM sensitivity significantly improved the SRT prediction (ΔR2 = .13; total R2 = .44). The remaining unaccounted variance might be attributable to variability in cognitive function and other dimensions of suprathreshold distortion. STM sensitivity was most critical in predicting SRTs for listeners < 65 years old or with HFA <53 dB HL. Results are discussed in the context of previous work suggesting that STM sensitivity for low rates and low-frequency carriers is impaired by a reduced ability to use temporal fine-structure information to detect dynamic spectra. STM detection is a fast test of suprathreshold auditory function for frequencies <2 kHz that complements the HFA to predict variability in hearing-aid outcomes for speech perception in noise.

Spectrotemporal Modulation Detection and Speech Perception by Cochlear Implant Users.

Spectrotemporal modulation (STM) detection performance was examined for cochlear implant (CI) users. The test involved discriminating between an unmodulated steady noise and a modulated stimulus. The modulated stimulus presents frequency modulation patterns that change in frequency over time. In order to examine STM detection performance for different modulation conditions, two different temporal modulation rates (5 and 10 Hz) and three different spectral modulation densities (0.5, 1.0, and 2.0 cycles/octave) were employed, producing a total 6 different STM stimulus conditions. In order to explore how electric hearing constrains STM sensitivity for CI users differently from acoustic hearing, normal-hearing (NH) and hearing-impaired (HI) listeners were also tested on the same tasks. STM detection performance was best in NH subjects, followed by HI subjects. On average, CI subjects showed poorest performance, but some CI subjects showed high levels of STM detection performance that was comparable to acoustic hearing. Significant correlations were found between STM detection performance and speech identification performance in quiet and in noise. In order to understand the relative contribution of spectral and temporal modulation cues to speech perception abilities for CI users, spectral and temporal modulation detection was performed separately and related to STM detection and speech perception performance. The results suggest that that slow spectral modulation rather than slow temporal modulation may be important for determining speech perception capabilities for CI users. Lastly, test–retest reliability for STM detection was good with no learning. The present study demonstrates that STM detection may be a useful tool to evaluate the ability of CI sound processing strategies to deliver clinically pertinent acoustic modulation information.

Spectrotemporal modulation sensitivity for hearing-impaired listeners: dependence on carrier center frequency and the relationship to speech intelligibility.

Poor speech understanding in noise by hearing-impaired (HI) listeners is only partly explained by elevated audiometric thresholds. Suprathreshold-processing impairments such as reduced temporal or spectral resolution or temporal fine-structure (TFS) processing ability might also contribute. Although speech contains dynamic combinations of temporal and spectral modulation and TFS content, these capabilities are often treated separately. Modulation-depth detection thresholds for spectrotemporal modulation (STM) applied to octave-band noise were measured for normal-hearing and HI listeners as a function of temporal modulation rate (4-32 Hz), spectral ripple density [0.5-4 cycles/octave (c/o)] and carrier center frequency (500-4000 Hz). STM sensitivity was worse than normal for HI listeners only for a low-frequency carrier (1000 Hz) at low temporal modulation rates (4-12 Hz) and a spectral ripple density of 2 c/o, and for a high-frequency carrier (4000 Hz) at a high spectral ripple density (4 c/o). STM sensitivity for the 4-Hz, 4-c/o condition for a 4000-Hz carrier and for the 4-Hz, 2-c/o condition for a 1000-Hz carrier were correlated with speech-recognition performance in noise after partialling out the audiogram-based speech-intelligibility index. Poor speech-reception and STM-detection performance for HI listeners may be related to a combination of reduced frequency selectivity and a TFS-processing deficit limiting the ability to track spectral-peak movements.

Spectrotemporal Modulation Sensitivity as a Predictor of Speech Intelligibility for Hearing-Impaired Listeners

A model that can accurately predict speech intelligibility for a given hearing-impaired (HI) listener would be an important tool for hearing-aid fitting or hearing-aid algorithm development. Existing speech-intelligibility models do not incorporate variability in suprathreshold deficits that are not well predicted by classical audiometric measures. One possible approach to the incorporation of such deficits is to base intelligibility predictions on sensitivity to simultaneously spectrally and temporally modulated signals. The likelihood of success of this approach was evaluated by comparing estimates of spectrotemporal modulation (STM) sensitivity to speech intelligibility and to psychoacoustic estimates of frequency selectivity and temporal fine-structure (TFS) sensitivity across a group of HI listeners. The minimum modulation depth required to detect STM applied to an 86 dB SPL four-octave noise carrier was measured for combinations of temporal modulation rate (4, 12, or 32 Hz) and spectral modulation density (0.5, 1, 2, or 4 cycles/octave). STM sensitivity estimates for individual HI listeners were compared to estimates of frequency selectivity (measured using the notched-noise method at 500, 1000, 2000, and 4000 Hz), TFS processing ability (2 Hz frequency-modulation detection thresholds for 500, 1000, 2000, and 4000 Hz carriers) and sentence intelligibility in noise (at a 0 dB signal-to-noise ratio) that were measured for the same listeners in a separate study. Eight normal-hearing (NH) listeners and 12 listeners with a diagnosis of bilateral sensorineural hearing loss participated. STM sensitivity was compared between NH and HI listener groups using a repeated-measures analysis of variance. A stepwise regression analysis compared STM sensitivity for individual HI listeners to audiometric thresholds, age, and measures of frequency selectivity and TFS processing ability. A second stepwise regression analysis compared speech intelligibility to STM sensitivity and the audiogram-based Speech Intelligibility Index. STM detection thresholds were elevated for the HI listeners, but only for low rates and high densities. STM sensitivity for individual HI listeners was well predicted by a combination of estimates of frequency selectivity at 4000 Hz and TFS sensitivity at 500 Hz but was unrelated to audiometric thresholds. STM sensitivity accounted for an additional 40% of the variance in speech intelligibility beyond the 40% accounted for by the audibility-based Speech Intelligibility Index. Impaired STM sensitivity likely results from a combination of a reduced ability to resolve spectral peaks and a reduced ability to use TFS information to follow spectral-peak movements. Combining STM sensitivity estimates with audiometric threshold measures for individual HI listeners provided a more accurate prediction of speech intelligibility than audiometric measures alone. These results suggest a significant likelihood of success for an STM-based model of speech intelligibility for HI listeners.