Amplitude Modulation Detection Thresholds Research Articles

Disentangling the effects of hearing loss and age on amplitude modulation frequency selectivity.

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.

Behavioral characterization of the cochlear amplifier lesion due to loss of function of stereocilin (STRC) in human subjects

Loss of function of stereocilin (STRC) is the second most common cause of inherited hearing loss. The loss of the stereocilin protein, encoded by the STRC gene, induces the loss of connection between outer hair cells and tectorial membrane. This only affects the outer hair cells (OHCs) function, involving deficits of active cochlear frequency selectivity and amplifier functions despite preservation of normal inner hair cells. Better understanding of cochlear features associated with mutation of STRC will improve our knowledge of normal cochlear function, the pathophysiology of hearing impairment, and potentially enhance hearing aid and cochlear implant signal processing. Nine subjects with homozygous or compound heterozygous loss of function mutations in STRC were included, age 7–24 years. Temporal and spectral modulation perception were measured, characterized by spectral and temporal modulation transfer functions. Speech-in-noise perception was studied with spondee identification in adaptive steady-state noise and AzBio sentences with 0 and -5 dB SNR multitalker babble. Results were compared with normal hearing (NH) and cochlear implant (CI) listeners to place STRC−/− listeners’ hearing capacity in context. Spectral ripple discrimination thresholds in the STRC−/− subjects were poorer than in NH listeners (p < 0.0001) but remained better than for CI listeners (p < 0.0001). Frequency resolution appeared impaired in the STRC−/− group compared to NH listeners but did not reach statistical significance (p = 0.06). Compared to NH listeners, amplitude modulation detection thresholds in the STRC−/− group did not reach significance (p= 0.06) but were better than in CI subjects (p < 0.0001). Temporal resolution in STRC−/− subjects was similar to NH (p = 0.98) but better than in CI listeners (p = 0.04). The spondee reception threshold in the STRC−/− group was worse than NH listeners (p = 0.0008) but better than CI listeners (p = 0.0001). For AzBio sentences, performance at 0 dB SNR was similar between the STRC−/− group and the NH group, 88 % and 97 % respectively. For -5 dB SNR, the STRC−/− performance was significantly poorer than NH, 40 % and 85 % respectively, yet much better than with CI who performed at 54 % at +5 dB SNR in children and 53 % at + 10 dB SNR in adults. To our knowledge, this is the first study of the psychoacoustic performance of human subjects lacking cochlear amplification but with normal inner hair cell function. Our data demonstrate preservation of temporal resolution and a trend to impaired frequency resolution in this group without reaching statistical significance. Speech-in-noise perception compared to NH listeners was impaired as well. All measures were better than those in CI listeners. It remains to be seen if hearing aid modifications, customized for the spectral deficits in STRC−/− listeners can improve speech understanding in noise. Since cochlear implants are also limited by deficient spectral selectivity, STRC−/− hearing may provide an upper bound on what could be obtained with better temporal coding in electrical stimulation.

The Effect of Hemodialysis on Spectral and Temporal Processing Abilities and Speech Perception in Noise among Individuals with Chronic Kidney Disease

Introduction: The effect of chronic kidney disease (CKD) on hearing is well documented in the literature. Several studies have investigated the effect of hemodialysis on the peripheral auditory system among individuals with CKD. However, studies investigating the effect of hemodialysis on speech perception and auditory processing abilities are limited. The present study investigated the effect of hemodialysis on few auditory processing abilities and speech perception in noise among adults with CKD. Methods: A total of 25 adults with CKD undergoing hemodialysis regularly participated in the study. Spectral ripple discrimination threshold (SRDT), gap detection threshold (GDT), amplitude-modulation detection threshold (AMDT), and speech recognition threshold in noise (SRTn) were measured before and after hemodialysis. Paired samples “t” test was carried out to investigate the effect of hemodialysis on thresholds. Results: Results showed a significant improvement for SRDT, GDT, AMDT, and SRTn after hemodialysis among individuals with CKD. Discussion: Hemodialysis showed a positive effect on speech perception in noise and auditory processing abilities among individuals with CKD.

Neuronal responses in mouse inferior colliculus correlate with behavioral detection of amplitude-modulated sound.

Amplitude modulation (AM) is a common feature of natural sounds, including speech and animal vocalizations. Here, we used operant conditioning and in vivo electrophysiology to determine the AM detection threshold of mice as well as its underlying neuronal encoding. Mice were trained in a Go-NoGo task to detect the transition to AM within a noise stimulus designed to prevent the use of spectral side-bands or a change in intensity as alternative cues. Our results indicate that mice, compared with other species, detect high modulation frequencies up to 512 Hz well, but show much poorer performance at low frequencies. Our in vivo multielectrode recordings in the inferior colliculus (IC) of both anesthetized and awake mice revealed a few single units with remarkable phase-locking ability to 512 Hz modulation, but not sufficient to explain the good behavioral detection at that frequency. Using a model of the population response that combined dimensionality reduction with threshold detection, we reproduced the general band-pass characteristics of behavioral detection based on a subset of neurons showing the largest firing rate change (both increase and decrease) in response to AM, suggesting that these neurons are instrumental in the behavioral detection of AM stimuli by the mice.NEW & NOTEWORTHY The amplitude of natural sounds, including speech and animal vocalizations, often shows characteristic modulations. We examined the relationship between neuronal responses in the mouse inferior colliculus and the behavioral detection of amplitude modulation (AM) in sound and modeled how the former can give rise to the latter. Our model suggests that behavioral detection can be well explained by the activity of a subset of neurons showing the largest firing rate changes in response to AM.

Tests of human auditory temporal resolution: preliminary investigation of ZEST parameters for amplitude modulation detection.

Auditory temporal resolution plays a critical role in the everyday experience of listening to complex acoustic patterns. Amplitude modulation detection thresholds are widely used to measure auditory temporal resolution. In an attempt to develop a standardized clinical test of auditory temporal resolution, we used ZEST (Zippy Estimation by Sequential Testing, a Bayesian threshold estimation procedure, to measure amplitude modulation detection thresholds. ZEST utilizes prior knowledge about a listener's thresholds, as represented by a probability density function of the thresholds, and psychometric functions of the listener's responses. This paper reports a preliminary study in which ZEST parameters that could be used for measurements of amplitude modulation detection thresholds were sought. For this purpose, we created histograms of the detection thresholds for a wide range of modulation frequencies, measured the psychometric functions of amplitude modulation detection, and performed computer simulations of ZEST threshold estimation. The results suggested that, with appropriately-set parameters, ZEST allows for the accurate estimation of amplitude modulation detection thresholds within 20 trials.

The effect of recreational noise exposure on amplitude-modulation detection, hearing sensitivity at frequencies above 8 kHz, and perception of speech in noise.

Psychoacoustic and speech perception measures were compared for a group who were exposed to noise regularly through listening to music via personal music players (PMP) and a control group without such exposure. Lifetime noise exposure, quantified using the NESI questionnaire, averaged ten times higher for the exposed group than for the control group. Audiometric thresholds were similar for the two groups over the conventional frequency range up to 8 kHz, but for higher frequencies, the exposed group had higher thresholds than the control group. Amplitude modulation detection (AMD) thresholds were measured using a 4000-Hz sinusoidal carrier presented in threshold-equalizing noise at 30, 60, and 90 dB sound pressure level (SPL) for modulation frequencies of 8, 16, 32, and 64 Hz. At 90 dB SPL but not at the lower levels, AMD thresholds were significantly higher (worse) for the exposed than for the control group, especially for low modulation frequencies. The exposed group required significantly higher signal-to-noise ratios than the control group to understand sentences in noise. Otoacoustic emissions did not differ for the two groups. It is concluded that listening to music via PMP can have subtle deleterious effects on speech perception, AM detection, and hearing sensitivity over the extended high-frequency range.

Suprathreshold auditory processes in listeners with normal audiograms but extended high-frequency hearing loss

Hearing loss in the extended high-frequency (EHF) range (>8 kHz) is widespread among young normal-hearing adults and could have perceptual consequences such as difficulty understanding speech in noise. However, it is unclear how EHF hearing loss might affect basic psychoacoustic processes. The hypothesis that EHF hearing loss is associated with poorer auditory resolution in the standard frequencies was tested. Temporal resolution was characterized by amplitude modulation detection thresholds (AMDTs), and spectral resolution was characterized by frequency change detection thresholds (FCDTs). AMDTs and FCDTs were measured in adults with or without EHF loss but with normal clinical audiograms. AMDTs were measured with 0.5- and 4-kHz carrier frequencies; similarly, FCDTs were measured for 0.5- and 4-kHz base frequencies. AMDTs were significantly higher with the 4 kHz than the 0.5 kHz carrier, but there was no significant effect of EHF loss. There was no significant effect of EHF loss on FCDTs at 0.5 kHz; however, FCDTs were significantly higher at 4 kHz for listeners with than without EHF loss. This suggests that some aspects of auditory resolution in the standard audiometric frequency range may be compromised in listeners with EHF hearing loss despite having a normal audiogram.

Modulation masking produced by a low-frequency pure tone

An intense low-frequency tone can affect the perception of amplitude modulation (AM) applied to a high-frequency carrier. Here, thresholds for detecting AM of a 3000-Hz carrier were measured in the presence of a 50-Hz pure tone at 91 dB SPL. When the carrier was presented at 20 dB sensation level (SL), the thresholds were higher than in the absence of the 50-Hz tone, increased when the AM frequency was increased from 20 to 100 Hz, and did not show a maximum near 50 Hz, as would be expected if the effect of the 50-Hz tone resulted from modulation detection interference. When the AM frequency was fixed at 50 Hz, the AM detection thresholds showed a minimum when the phase of the AM was 90° ahead of the phase of the 50-Hz tone (denoted Δφ = 90°) and a maximum for Δφ = 270°. To assess the role of the outer hair cells (OHCs), AM detection thresholds were measured as a function of Δφ using SLs of 20 and 50 dB for normal-hearing participants and 20 dB for hearing-impaired participants. It was assumed that the latter would have impaired OHC function. The pattern of the results was similar across SLs and groups: AM detection thresholds were 8–10 dB lower for Δφ = 90° than for Δφ = 270° in all cases. This suggests that the OHCs do not play a large role in these effects and supports the idea that the low-frequency tone biases the responses of inner hair cells tuned to high frequencies.

Temporal processing, spectral processing, and speech perception in noise abilities among individuals with chronic kidney disease undergoing hemodialysis

Background In the literature, the effect of chronic kidney disease on the peripheral auditory system has been well documented. But studies investigating the effect of chronic kidney disease on speech perception and auditory processing abilities are limited. Aims/objectives The present study investigated the effect of chronic kidney disease on different auditory processing tasks and speech perception in noise among adults. Material and methods A total of 28 adults participated in the study. Group 1 included 14 individuals with chronic kidney disease undergoing hemodialysis, and Group 2 included 14 individuals with no known kidney complications. Amplitude modulation detection threshold, gap detection threshold, spectral ripple discrimination threshold, and speech recognition threshold in noise were measured. Independent samples t-test was carried out to investigate whether mean thresholds are significantly different between groups. Results Results showed poorer gap detection threshold, amplitude modulation detection threshold, spectral ripple discrimination threshold, and speech recognition threshold in noise among individuals with chronic kidney disease compared to individuals with no known kidney complications. Conclusions The present study showed poorer auditory processing and speech perception abilities in individuals with chronic kidney disease.

Effect of Realistic Test Conditions on Spectral and Temporal Processing in Normal-Hearing Listeners.

Purpose To measure the effect of testing conditions (in the soundproof booth vs. quiet room), test order, and number of test sessions on spectral and temporal processing in normal-hearing (NH) listeners. Method Thirty-two adult NH listeners participated in the three experiments. For all three experiments, the stimuli were presented to the left ear at the subjects' most comfortable level through headphones. All tests were administered in an adaptive three-alternative forced-choice paradigm. Experiment 1 was designed to compare the effect of soundproof booth and quiet room test conditions on amplitude modulation detection threshold and modulation frequency discrimination threshold with each of the five modulation frequencies. Experiment 2 was designed to compare the effect of two test orders on the frequency discrimination thresholds under the quiet room test conditions. The thresholds were first measured in the ascending and descending order of four pure tones, and then with counterbalanced order. For Experiment 3, the amplitude discrimination threshold under the quiet room testing condition was assessed 3 times to determine the effect of the number of test sessions. Then the thresholds were compared over the sessions. Results Results showed no significant effect of test environment. The test order is an important variable for frequency discrimination, particularly between piano tunes and pure tones. Results also show no significant difference across test sessions. Conclusions These results suggest that a controlled test environment may not be required in spectral and temporal assessment for NH listeners. Under the quiet test environment, a single outcome measure is sufficient, but test orders should be counterbalanced.

Effects of noise precursors on the detection of amplitude and frequency modulation for tones in noise.

Recent studies on amplitude modulation (AM) detection for tones in noise reported that AM-detection thresholds improve when the AM stimulus is preceded by a noise precursor. The physiological mechanisms underlying this AM unmasking are unknown. One possibility is that adaptation to the level of the noise precursor facilitates AM encoding by causing a shift in neural rate-level functions to optimize level encoding around the precursor level. The aims of this study were to investigate whether such a dynamic-range adaptation is a plausible mechanism for the AM unmasking and whether frequency modulation (FM), thought to be encoded via AM, also exhibits the unmasking effect. Detection thresholds for AM and FM of tones in noise were measured with and without a fixed-level precursor. Listeners showing the unmasking effect were then tested with the precursor level roved over a wide range to modulate the effect of adaptation to the precursor level on the detection of the subsequent AM. It was found that FM detection benefits from a precursor and the magnitude of FM unmasking correlates with that of AM unmasking. Moreover, consistent with dynamic-range adaptation, the unmasking magnitude weakens as the level difference between the precursor and simultaneous masker of the tone increases.

Acoustic Change Responses to Amplitude Modulation in Cochlear Implant Users: Relationships to Speech Perception.

ObjectivesThe ability to understand speech is highly variable in people with cochlear implants (CIs) and to date, there are no objective measures that identify the root of this discrepancy. However, behavioral measures of temporal processing such as the temporal modulation transfer function (TMTF) has previously found to be related to vowel and consonant identification in CI users. The acoustic change complex (ACC) is a cortical auditory-evoked potential response that can be elicited by a “change” in an ongoing stimulus. In this study, the ACC elicited by amplitude modulation (AM) change was related to measures of speech perception as well as the amplitude detection threshold in CI users.MethodsTen CI users (mean age: 50 years old) participated in this study. All subjects participated in behavioral tests that included both speech and amplitude modulation detection to obtain a TMTF. CI users were categorized as “good” (n = 6) or “poor” (n = 4) based on their speech-in noise score (<50%). 64-channel electroencephalographic recordings were conducted while CI users passively listened to AM change sounds that were presented in a free field setting. The AM change stimulus was white noise with four different AM rates (4, 40, 100, and 300 Hz).ResultsBehavioral results show that AM detection thresholds in CI users were higher compared to the normal-hearing (NH) group for all AM rates. The electrophysiological data suggest that N1 responses were significantly decreased in amplitude and their latencies were increased in CI users compared to NH controls. In addition, the N1 latencies for the poor CI performers were delayed compared to the good CI performers. The N1 latency for 40 Hz AM was correlated with various speech perception measures.ConclusionOur data suggest that the ACC to AM change provides an objective index of speech perception abilities that can be used to explain some of the variation in speech perception observed among CI users.

A comparison of temporal processing and spectral processing abilities of monolingual, bilingual and multilingual children

Objective: This study examined the effects of bilingualism and multilingualism on supra-threshold auditory processing abilities in children.Design: Cross-sectional study.Study sample: Ninety children participated in the study, based on the number of languages they know children were assigned into three groups, i.e. monolingual, bilingual and multilingual. Amplitude modulation detection threshold, gap detection threshold, pitch discrimination threshold and spectral ripple discrimination threshold were measured.Results: Results showed superior supra-threshold auditory processing abilities among multilingual and bilingual children than monolingual children. The results further showed that, the supra-threshold auditory processing of multilingual children was better than bilingual children.Conclusion: This finding suggests that knowledge of multiple languages improves supra-threshold auditory processing abilities. This study adds to the growing body of literature supporting the superior supra-threshold auditory processing abilities among bilingual and multilingual individuals.

Impact of Aging and the Electrode-to-Neural Interface on Temporal Processing Ability in Cochlear-Implant Users: Amplitude-Modulation Detection Thresholds.

Although cochlear implants (CIs) are a viable treatment option for severe hearing loss in adults of any age, older adults may be at a disadvantage compared with younger adults. CIs deliver signals that contain limited spectral information, requiring CI users to attend to the temporal information within the signal to recognize speech. Older adults are susceptible to acquiring auditory temporal processing deficits, presenting a potential age-related limitation for recognizing speech signals delivered by CIs. The goal of this study was to measure auditory temporal processing ability via amplitude-modulation (AM) detection as a function of age in CI users. The contribution of the electrode-to-neural interface, in addition to age, was estimated using electrically evoked compound action potential (ECAP) amplitude growth functions. Within each participant, two electrodes were selected: one with the steepest ECAP slope and one with the shallowest ECAP slope, in order to represent electrodes with varied estimates of the electrode-to-neural interface. Single-electrode AM detection thresholds were measured using direct stimulation at these two electrode locations. Results revealed that AM detection ability significantly declined as a function of chronological age. ECAP slope did not significantly impact AM detection, but ECAP slope decreased (became shallower) with increasing age, suggesting that factors influencing the electrode-to-neural interface change with age. Results demonstrated a significant negative impact of chronological age on auditory temporal processing. The locus of the age-related limitation (peripheral vs. central origin), however, is difficult to evaluate because the peripheral influence (ECAPs) was correlated with the central factor (age).

Development of temporal auditory processing in childhood: Changes in efficiency rather than temporal-modulation selectivity.

The ability to detect amplitude modulation (AM) is essential to distinguish the spectro-temporal features of speech from those of a competing masker. Previous work shows that AM sensitivity improves until 10 years of age. This may relate to the development of sensory factors (tuning of AM filters, susceptibility to AM masking) or to changes in processing efficiency (reduction in internal noise, optimization of decision strategies). To disentangle these hypotheses, three groups of children (5-11 years) and one of young adults completed psychophysical tasks measuring thresholds for detecting sinusoidal AM (with a rate of 4, 8, or 32 Hz) applied to carriers whose inherent modulations exerted different amounts of AM masking. Results showed that between 5 and 11 years, AM detection thresholds improved and that susceptibility to AM masking slightly increased. However, the effects of AM rate and carrier were not associated with age, suggesting that sensory factors are mature by 5 years. Subsequent modelling indicated that reducing internal noise by a factor 10 accounted for the observed developmental trends. Finally, children's consonant identification thresholds in noise related to some extent to AM sensitivity. Increased efficiency in AM detection may support better use of temporal information in speech during childhood.

Adaptation to noise in amplitude modulation detection without the medial olivocochlear reflex

The detection of amplitude modulation (AM) in quiet or in noise improves when the AM carrier is preceded by noise, an effect that has been attributed to the medial olivocochlear reflex (MOCR). We investigate whether this improvement can occur without the MOCR by measuring AM sensitivity for cochlear implant (CI) users, whose MOCR effects are circumvented as a result of the electrical stimulation provided by the CI. AM detection thresholds were measured monaurally for short (50 ms) AM probes presented at the onset (early condition) or delayed by 300 ms (late condition) from the onset of a broadband noise. The noise was presented ipsilaterally, contralaterally and bilaterally to the test ear. Stimuli were processed through an experimental, time-invariant sound processing strategy. On average, thresholds were 4 dB better in the late than in the early condition and the size of the improvement was similar for the three noise lateralities. The pattern and magnitude of the improvement was broadly consistent with that for normal hearing listeners [Marrufo-Pérez et al., 2018, J Assoc Res Otolaryngol 19:147–161]. Because the electrical stimulation provided by CIs is independent from the middle-ear muscle reflex (MEMR) or the MOCR, this shows that mechanisms other than the MEMR or the MOCR can facilitate AM detection in noisy backgrounds.

Age-related differences in modulation detection interference and interference release

Age-related declines have been observed in auditory tasks related to temporal processing, but less work has been conducted in middle-aged listeners and in auditory sound segregation tasks. This experiment addresses these issues by evaluating modulation detection interference (MDI) and release from MDI using streaming in young, middle-aged and older listeners. Using a standard MDI paradigm, we measured amplitude modulation detection thresholds of a high-frequency tone in different conditions: in quiet, in the presence of a low-impact unmodulated interferer, and in the presence of a high-impact modulated interferer. Then, we measured streaming-based release from MDI using four modulated precursors designed to perceptually capture the interferer and therefore reduce the amount of interference. Preliminary data suggest that middle-aged normal-hearing listeners experience similar MDI to young listeners and also receive a large release from interference when precursors are present. Additional data will be presented from older listeners, who experience slightly greater MDI than younger listeners.

Effects of Age and Noise Exposure on Proxy Measures of Cochlear Synaptopathy.

Although there is strong histological evidence for age-related synaptopathy in humans, evidence for the existence of noise-induced cochlear synaptopathy in humans is inconclusive. Here, we sought to evaluate the relative contributions of age and noise exposure to cochlear synaptopathy using a series of electrophysiological and behavioral measures. We extended an existing cohort by including 33 adults in the age range 37 to 60, resulting in a total of 156 participants, with the additional older participants resulting in a weakening of the correlation between lifetime noise exposure and age. We used six independent regression models (corrected for multiple comparisons), in which age, lifetime noise exposure, and high-frequency audiometric thresholds were used to predict measures of synaptopathy, with a focus on differential measures. The models for auditory brainstem responses, envelope-following responses, interaural phase discrimination, and the co-ordinate response measure of speech perception were not statistically significant. However, both age and noise exposure were significant predictors of performance on the digit triplet test of speech perception in noise, with greater noise exposure (unexpectedly) predicting better performance in the 80 dB sound pressure level (SPL) condition and greater age predicting better performance in the 40 dB SPL condition. Amplitude modulation detection thresholds were also significantly predicted by age, with older listeners performing better than younger listeners at 80 dB SPL. Overall, the results are inconsistent with the predicted effects of synaptopathy.

Sensorineural hearing loss impairs sensitivity but spares temporal integration for detection of frequency modulation.

The effect of the number of modulation cycles (N) on frequency-modulation (FM) detection thresholds (FMDTs) was measured with and without interfering amplitude modulation (AM) for hearing-impaired (HI) listeners, using a 500-Hz sinusoidal carrier and FM rates of 2 and 20 Hz. The data were compared with FMDTs for normal-hearing (NH) listeners and AM detection thresholds (AMDTs) for NH and HI listeners [Wallaert, Moore, and Lorenzi (2016). J. Acoust. Soc. 139, 3088-3096; Wallaert, Moore, Ewert, and Lorenzi (2017). J. Acoust. Soc. 141, 971-980]. FMDTs were higher for HI than for NH listeners, but the effect of increasing N was similar across groups. In contrast, AMDTs were lower and the effect of increasing N was greater for HI listeners than for NH listeners. A model of temporal-envelope processing based on a modulation filter-bank and a template-matching decision strategy accounted better for the FMDTs at 20 Hz than at 2 Hz for young NH listeners and predicted greater temporal integration of FM than observed for all groups. These results suggest that different mechanisms underlie AM and FM detection at low rates and that hearing loss impairs FM-detection mechanisms, but preserves the memory and decision processes responsible for temporal integration of FM.

Amplitude modulation detection with a short-duration carrier: Effects of a precursor and hearing loss.

This study tests the hypothesis that amplitude modulation (AM) detection will be better under conditions where basilar membrane (BM) response growth is expected to be linear rather than compressive. This hypothesis was tested by (1) comparing AM detection for a tonal carrier as a function of carrier level for subjects with and without cochlear hearing impairment (HI), and by (2) comparing AM detection for carriers presented with and without an ipsilateral notched-noise precursor, under the assumption that the precursor linearizes BM responses. Average AM detection thresholds were approximately 5 dB better for subjects with HI than for subjects with normal hearing (NH) at moderate-level carriers. Average AM detection for low-to-moderate level carriers was approximately 2 dB better with the precursor than without the precursor for subjects with NH, whereas precursor effects were absent or smaller for subjects with HI. Although effect sizes were small and individual differences were noted, group differences are consistent with better AM detection for conditions where BM responses are less compressive due to cochlear hearing loss or due to a reduction in cochlear gain. These findings suggest the auditory system may quickly adjust to the local soundscape to increase effective AM depth and improve signal-to-noise ratios.