Comodulation Masking Release Research Articles

Monaural and binaural masking release with speech-like stimuli.

The relevance of comodulation and interaural phase difference for speech perception is still unclear. We used speech-like stimuli to link spectro-temporal properties of formants with masking release. The stimuli comprised a tone and three masker bands centered at formant frequencies F1, F2, and F3 derived from a consonant-vowel. The target was a diotic or dichotic frequency-modulated tone following F2 trajectories. Results showed a small comodulation masking release, while the binaural masking level difference was comparable to previous findings. The data suggest that factors other than comodulation may play a dominant role in grouping frequency components in speech.

Evidence for proactive and retroactive temporal pattern analysis in simultaneous maskinga).

Amplitude modulation (AM) of a masker reduces its masking on a simultaneously presented unmodulated pure-tone target, which likely involves dip listening. This study tested the idea that dip-listening efficiency may depend on stimulus context, i.e., the match in AM peakedness (AMP) between the masker and a precursor or postcursor stimulus, assuming a form of temporal pattern analysis process. Masked thresholds were measured in normal-hearing listeners using Schroeder-phase harmonic complexes as maskers and precursors or postcursors. Experiment 1 showed threshold elevation (i.e., interference) when a flat cursor preceded or followed a peaked masker, suggesting proactive and retroactive temporal pattern analysis. Threshold decline (facilitation) was observed when the masker AMP was matched to the precursor, irrespective of stimulus AMP, suggesting only proactive processing. Subsequent experiments showed that both interference and facilitation (1) remained robust when a temporal gap was inserted between masker and cursor, (2) disappeared when an F0-difference was introduced between masker and precursor, and (3) decreased when the presentation level was reduced. These results suggest an important role of envelope regularity in dip listening, especially when masker and cursor are F0-matched and, therefore, form one perceptual stream. The reported effects seem to represent a time-domain variant of comodulation masking release.

Web-based psychoacoustics: Hearing screening, infrastructure, and validation

Anonymous web-based experiments are increasingly used in many domains of behavioral research. However, online studies of auditory perception, especially of psychoacoustic phenomena pertaining to low-level sensory processing, are challenging because of limited available control of the acoustics, and the inability to perform audiometry to confirm normal-hearing status of participants. Here, we outline our approach to mitigate these challenges and validate our procedures by comparing web-based measurements to lab-based data on a range of classic psychoacoustic tasks. Individual tasks were created using jsPsych, an open-source JavaScript front-end library. Dynamic sequences of psychoacoustic tasks were implemented using Django, an open-source library for web applications, and combined with consent pages, questionnaires, and debriefing pages. Subjects were recruited via Prolific, a subject recruitment platform for web-based studies. Guided by a meta-analysis of lab-based data, we developed and validated a screening procedure to select participants for (putative) normal-hearing status based on their responses in a suprathreshold task and a survey. Headphone use was standardized by supplementing procedures from prior literature with a binaural hearing task. Individuals meeting all criteria were re-invited to complete a range of classic psychoacoustic tasks. For the re-invited participants, absolute thresholds were in excellent agreement with lab-based data for fundamental frequency discrimination, gap detection, and sensitivity to interaural time delay and level difference. Furthermore, word identification scores, consonant confusion patterns, and co-modulation masking release effect also matched lab-based studies. Our results suggest that web-based psychoacoustics is a viable complement to lab-based research. Source code for our infrastructure is provided.

Comodulation Masking Release in Tinnitus Frequency and One Lower Octave of Tinnitus Frequency.

Inhibitory function is the basis of many perceptual and non-perceptual abilities in the auditory system. In people with tinnitus, decreased inhibitory function in the central auditory system has been proven. This disorder is caused by an increase in neural activity caused by an imbalance between stimulation and inhibition. The aim of this study was to evaluate and compare inhibitory function in persons who had tinnitus, at and one octave lower than the tinnitus frequency. Studies show that inhibition has very important role in comodulation masking release. According to inhibitory dysfunction in people with tinnitus, in this study we assessed comodulation masking release in tinnitus frequency and one lower octave. Participants were divided into two groups. Group 1 consisted of 7 individuals with unilateral tonal tinnitus at 4kHz and group 2 included 7 individuals with unilateral tonal tinnitus at 6kHz. Paired test, in each group separately, showed that the comodulation masking release and Across Frequency comodulation masking release differed significantly between tinnitus frequency and one octave lower in each group (p < 0.05). In fact, the disinhibition in the area around the frequency of the tinnitus seems to be greater than the tinnitus frequency area. It seems that the results of CMRs can be used in planning and managing the treatment of people with tinnitus (such as sound therapy, etc.).

Modelling suppression and comodulation masking release using the dual-resonance nonlinear filter.

Although comodulation masking release (CMR) is commonly associated with across-channel processes, it was often argued that part of the effect may be explained by processing within an auditory filter. One peripheral mechanism for such within-channel process is cochlear suppression. Using the dual-resonance nonlinear filter model with different sets of model parameters, the present study shows that the simulated CMR is associated with the simulated two-tone suppression. A modification of the model parameters results in a more accurate prediction of suppression and thus, is also more accurate in predicting the contribution of suppression to CMR.

Auditory masking in killer whales (Orcinus orca) with realistic signals and noise

Killer whales are the largest delphinid odontocete, a top predator and are globally distributed. Southern resident killer whales, which inhabit the Pacific coastal region of the northwest United States and Canada, are listed as endangered. Anthropogenic noise has been identified as a major threat to this populations of killer whales. This paper will cover recent results from killer whale auditory masking experiments using a variety of signals and noise types. Signal types included pure tones and recordings of killer whale calls. Noise types included Gaussian noise and recordings of seismic surveys and continuous active sonar. Potential auditory mechanisms that govern the resulting masking patterns, including dip listening, off-frequency listening, and comodulation masking release are discussed. These data will help to better understand and predict how killer whales can acoustically communicate, navigate, and locate prey in an increasingly noisy environment.

Comodulation masking release with random variations of flanking-band center frequencies.

Comodulation masking release (CMR) is an effect that is associated with auditory sensitivity to coherent amplitude modulations in different frequency regions. The present study investigated if this comodulation is detected by a direct comparison of auditory filter outputs, or if common masker fluctuations are first extracted by a broadly tuned stage that integrates information across a large spectral range. To this end, a modified flanking-band experiment with a narrowband noise masker at the signal frequency (on-frequency masker), and two flanking bands (FBs), one centered below and one above the signal frequency, were used. The center frequencies (CFs) of FBs changed whenever the masker had a local envelope minimum. The center frequencies were randomly chosen from a range of frequencies around the average CF of each FB. A CMR was measured even for large CF variations of FBs, where the envelopes at the off-frequency auditory filters were no longer the same as the masker envelope at the on-frequency auditory filter. This supports the hypothesis of a broadly tuned stage to determine masker comodulation. For two experimental settings, CMR deteriorated for very large variations of CFs of FBs, suggesting a spectral weighting of the off-frequency auditory filters in this broadly tuned stage.

Comodulation masking release effect in children with and without dyslexia

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Speech recognition in a modulating noise background can be facilitated by a process attributable to comodulation masking release (CMR). CMR is usually assumed to depend on comparisons of the outputs of different auditory filters. There was an immense importance to study to find the CMR effect in children with and without dyslexia.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; The study was to find the CMR effect in children with and without dyslexia. The current research was carried out through five steps i.e. auditory attention task stimuli preparation, auditory performance test, CMR stimuli preparation, CMR task and statistical analysis. Through these processes for measuring the CMR was done for the children with and without dyslexia. All the data were tabulated and statistically computed for the analysis of the data. SPSS software version 16 was used for the statistical analysis of the data. &lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Independent t-test was used for the statistical analysis while the comparison between groups. Paired t- test was used for the statistical analysis while the comparison within the group at 95% confidence interval. These results indicated that the amount effect of CMR is greater in children with dyslexia. There was not a significant difference of CMR between the children with and without dyslexia to the effect of CMR was not significantly different between the ears in children without dyslexia and with dyslexia.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; The present study indicates that children with dyslexia have selective inability to use the temporal and spectral cues necessary for signal extraction in CMR.&lt;/p&gt;

The comparison of the comodulation masking release (CMR) in individuals with and without chronic tinnitus

In comodulation masking release (CMR), the auditory signal threshold improves when maskers far from the frequency of the target signal are coherently amplitude-modulated. Studies show that inhibitory function may play a role in CMR. In individuals who have tinnitus, decreasing inhibitory functioning in auditory central nervous system has been documented. Therefore, in this study, the purpose was to evaluate CMR in individuals suffering from tinnitus and compare CMR findings with those who do not have tinnitus. Seventeen normal-hearing individuals (without tinnitus) and 13 individuals having unilateral tonal tinnitus (4000 or 6000 Hz) with normal or near to normal hearing participated in this study. All participants were 20 to 50 years of age and underwent comodulated (CM), unmodulated (UM), and reference (RF) threshold measurements and then the CMRs (CMR and Across Frequency CMR; AF-CMR) were calculated. An ANOVA showed that the CM thresholds were statistically different between groups, while the RF and UM thresholds were not statistically different. CMR (CMR & AF-CMR) function was higher in those without tinnitus compared to unilateral tinnitus sufferers. Due to the inhibitory role of the auditory central nervous system in CMR, it appears that tinnitus and CMR both may be influenced by inhibitory function.

Masking release in temporally fluctuating noise depends on comodulation and overall level in Cope's gray treefrog.

Many animals communicate acoustically in large social aggregations. Among the best studied are frogs, in which males form large breeding choruses where they produce loud vocalizations to attract mates. Although chorus noise poses significant challenges to communication, it also possesses features, such as comodulation in amplitude fluctuations, that listeners may be evolutionarily adapted to exploit in order to achieve release from masking. This study investigated the extent to which the benefits of comodulation masking release (CMR) depend on overall noise level in Cope's gray treefrog (Hyla chrysoscelis). Masked signal recognition thresholds were measured in response to vocalizations in the presence of chorus-shaped noise presented at two levels. The noises were either unmodulated or modulated with an envelope that was correlated (comodulated) or uncorrelated (deviant) across the frequency spectrum. Signal-to-noise ratios (SNRs) were lower at the higher noise level, and this effect was driven by relatively lower SNRs in modulated conditions, especially the comodulated condition. These results, which confirm that frogs benefit from CMR in a level-dependent manner, are discussed in relation to previous studies of CMR in humans and animals and in light of implications of the unique amphibian inner ear for considerations of within-channel versus across-channel mechanisms.

Asymmetric Flankers in Comodulation Masking Release.

Background and ObjectivesDetection of auditory signals may be improved when maskers far from the frequency of the target signal are coherently amplitude-modulated. This improvement of signal detection is called comodulation masking release (CMR). In the CMR experiments, flankers have been usually arranged symmetrically. In practice, we will be confronted with a problem by using symmetric flankers due to the limited output of clinical audiometers, especially at high-frequency. We aimed to check whether flanker arrangement has any effect on the amount of CMR, especially when there is no flankers with a frequency higher than the signal.Subjects and MethodsEighteen normal hearing listeners ranging in age from 20 to 46 years old participated. Symmetric (2-2) and asymmetric (3-1 and 4-0) flankers were used and then the amount of CMR compared among them.ResultsOur results showed in the same numbers of flankers, there were no statistically CMR differences between symmetric and asymmetric arrangement. Also when we did not have a flanker at a frequency higher than the signal and all flankers were placed below the signal, there was no statistically difference with the symmetric arrangement.ConclusionsThe asymmetry of the flankers and also omitting the flankers with a frequency higher than the signal, have no effect on CMR results. We concluded that CMR can be considered by using clinical audiometer.

Brainstem Correlates of Comodulation Masking Release for Speech in Normal Hearing Adults

Background and ObjectivesWeak signals embedded in fluctuating masker can be perceived more efficiently than similar signals embedded in unmodulated masker. This release from masking is known as comodulation masking release (CMR). In this paper, we investigate, neural correlates of CMR in the human auditory brainstem.Subjects and MethodsA total of 26 normal hearing subjects aged 18-30 years participated in this study. First, the impact of CMR was quantified by a behavioral experiment. After that, the brainstem correlates of CMR was investigated by the auditory brainstem response to complex sounds (cABR) in comodulated (CM) and unmodulated (UM) masking conditions.ResultsThe auditory brainstem responses are less susceptible to degradation in response to the speech syllable /da/ in the CM noise masker in comparison with the UM noise masker. In the CM noise masker, frequency-following response (FFR) and fundamental frequency (F0) were correlated with better behavioral CMR. Furthermore, the subcortical response timing of subjects with higher CMR was less affected by the CM noise masker, having higher stimulus-to-noise response correlations over the FFR range.ConclusionsThe results of the present study revealed a significant link between brainstem auditory processes and CMR. The findings of the present study show that cABR provides objective information about the neural correlates of CMR for speech stimulus.

Masking release by combined spatial and masker-fluctuation effects in the open sound field.

In a complex auditory scene, signals of interest can be distinguished from masking sounds by differences in source location [spatial release from masking (SRM)] and by differences between masker-alone and masker-plus-signal envelopes. This study investigated interactions between those factors in release of masking of 700-Hz tones in an open sound field. Signal and masker sources were colocated in front of the listener, or the signal source was shifted 90° to the side. In Experiment 1, the masker contained a 25-Hz-wide on-signal band plus flanking bands having envelopes that were either mutually uncorrelated or were comodulated. Comodulation masking release (CMR) was largely independent of signal location at a higher masker sound level, but at a lower level CMR was reduced for the lateral signal location. In Experiment 2, a brief signal was positioned at the envelope maximum (peak) or minimum (dip) of a 50-Hz-wide on-signal masker. Masking was released in dip more than in peak conditions only for the 90° signal. Overall, open-field SRM was greater in magnitude than binaural masking release reported in comparable closed-field studies, and envelope-related release was somewhat weaker. Mutual enhancement of masking release by spatial and envelope-related effects tended to increase with increasing masker level.

Detection of tones of unexpected frequency in amplitude-modulated noise.

Detection of a tonal signal in amplitude-modulated noise can improve with increases in noise bandwidth if the pattern of amplitude fluctuations is uniform across frequency, a phenomenon termed comodulation masking release (CMR). Most explanations for CMR rely on an assumption that listeners monitor frequency channels both at and remote from the signal frequency in conditions that yield the effect. To test this assumption, detectability was assessed for signals presented at expected and unexpected frequencies in wideband amplitude-modulated noise. Detection performance was high even for signals of unexpected frequency, suggesting that listeners were monitoring multiple frequency channels, as has been assumed.

Musical Training Enhances Neural Processing of Comodulation Masking Release in the Auditory Brainstem.

Musical training strengthens segregation the target signal from background noise. Musicians have enhanced stream segregation, which can be considered a process similar to comodulation masking release. In the current study, we surveyed psychoacoustical comodulation masking release in musicians and non-musicians. We then recorded the brainstem responses to complex stimuli in comodulated and unmodulated maskers to investigate the effect of musical training on the neural representation of comodulation masking release for the first time. The musicians showed significantly greater amplitudes and earlier brainstem response timing for stimulus in the presence of comodulated maskers than non-musicians. In agreement with the results of psychoacoustical experiment, musicians showed greater comodulation masking release than non-musicians. These results reveal a physiological explanation for behavioral enhancement of comodulation masking release and stream segregation in musicians.

Comodulation Enhances Signal Detection via Priming of Auditory Cortical Circuits.

Acoustic environments are composed of complex overlapping sounds that the auditory system is required to segregate into discrete perceptual objects. The functions of distinct auditory processing stations in this challenging task are poorly understood. Here we show a direct role for mouse auditory cortex in detection and segregation of acoustic information. We measured the sensitivity of auditory cortical neurons to brief tones embedded in masking noise. By altering spectrotemporal characteristics of the masker, we reveal that sensitivity to pure tone stimuli is strongly enhanced in coherently modulated broadband noise, corresponding to the psychoacoustic phenomenon comodulation masking release. Improvements in detection were largest following priming periods of noise alone, indicating that cortical segregation is enhanced over time. Transient opsin-mediated silencing of auditory cortex during the priming period almost completely abolished these improvements, suggesting that cortical processing may play a direct and significant role in detection of quiet sounds in noisy environments.SIGNIFICANCE STATEMENT Auditory systems are adept at detecting and segregating competing sound sources, but there is little direct evidence of how this process occurs in the mammalian auditory pathway. We demonstrate that coherent broadband noise enhances signal representation in auditory cortex, and that prolonged exposure to noise is necessary to produce this enhancement. Using optogenetic perturbation to selectively silence auditory cortex during early noise processing, we show that cortical processing plays a crucial role in the segregation of competing sounds.

Comodulation masking release in the inferior colliculus by combined signal enhancement and masker reduction.

Auditory signals that contain coherent level fluctuations of a masker in different frequency regions enhance the detectability of an embedded sinusoidal target signal, an effect commonly known as comodulation masking release (CMR). Neural correlates have been proposed at different stages of the auditory system. While later stages seem to suppress the response to the masker, earlier stages are more likely to enhance their response to the signal when the masker is comodulated. Using a flanking band masking paradigm, the present study investigates how CMR is represented at the level of the inferior colliculus of the Mongolian gerbil. The responses to a target signal at various sound pressure levels in three different masking conditions were compared. In one condition the masker was a 10-Hz amplitude modulated sinusoid centered at the signal frequency while in the other two conditions six off-frequency carriers (flanking bands) were added. From 81 units 26 showed a change that enhanced the detectability of the signal if the temporal modulation of the added flanking bands was identical to that of the masker at the signal frequency compared to the other two masking conditions. This study shows that the response characteristics of these neurons represent an intermediate stage between the representation in the cochlear nucleus and the auditory cortex. This means that the response is increased during the signal intervals but is also decreased for the following masker portions.

Hearing Mechanisms and Noise Metrics Related to Auditory Masking in Bottlenose Dolphins (Tursiops truncatus).

Odontocete cetaceans are acoustic specialists that depend on sound to hunt, forage, navigate, detect predators, and communicate. Auditory masking from natural and anthropogenic sound sources may adversely affect these fitness-related capabilities. The ability to detect a tone in a broad range of natural, anthropogenic, and synthesized noise was tested with bottlenose dolphins using a psychophysical, band-widening procedure. Diverging masking patterns were found for noise bandwidths greater than the width of an auditory filter. Despite different noise types having equal-pressure spectral-density levels (95 dB re 1 μPa(2)/Hz), masked detection threshold differences were as large as 22 dB. Consecutive experiments indicated that noise types with increased levels of amplitude modulation resulted in comodulation masking release due to within-channel and across-channel auditory mechanisms. The degree to which noise types were comodulated (comodulation index) was assessed by calculating the magnitude-squared coherence between the temporal envelope from an auditory filter centered on the signal and temporal envelopes from flanking filters. Statistical models indicate that masked thresholds in a variety of noise types, at a variety of levels, can be explained with metrics related to the comodulation index in addition to the pressure spectral-density level of noise. This study suggests that predicting auditory masking from ocean noise sources depends on both spectral and temporal properties of the noise.

Comodulation masking release in an off-frequency masking paradigm.

Detection threshold of a sinusoidal signal masked by a broadband masker is lower when on- and off-frequency masker components have a correlated envelope, compared to a condition in which these masker components have different envelopes. This effect is commonly referred to as comodulation masking release (CMR). The present study investigated if there is a CMR in the absence of a masker component at the signal frequency, i.e., in an off-frequency masking paradigm. Thresholds were measured for a 500-Hz signal in the presence of a broadband masker with a spectral notch at the signal frequency. Thresholds were significantly lower for a (co-)modulated than for an unmodulated masker for all notch widths up to 400 Hz. An additional experiment showed that the particularly large CMR for the no-notch condition was due to the way the modulated masker was generated. No CMR was measured when the notched-noise masker was replaced by a pair of narrowband noises. The addition of more remote masker bands resulted in a CMR of about 3-4 dB. The notched-noise data were predicted on the basis of a modulation-filterbank model. The predictions of the narrowband noise conditions indicated that all mechanisms underlying CMR might still not be fully understood.

Assessing the effects of temporal coherence on auditory stream formation through comodulation masking release

Recent studies of auditory streaming have suggested that repeated synchronous onsets and offsets over time, referred to as "temporal coherence," provide a strong grouping cue between acoustic components, even when they are spectrally remote. This study uses a measure of auditory stream formation, based on comodulation masking release (CMR), to assess the conditions under which a loss of temporal coherence across frequency can lead to auditory stream segregation. The measure relies on the assumption that the CMR, produced by flanking bands remote from the masker and target frequency, only occurs if the masking and flanking bands form part of the same perceptual stream. The masking and flanking bands consisted of sequences of narrowband noise bursts, and the temporal coherence between the masking and flanking bursts was manipulated in two ways: (a) By introducing a fixed temporal offset between the flanking and masking bands that varied from zero to 60 ms and (b) by presenting the flanking and masking bursts at different temporal rates, so that the asynchronies varied from burst to burst. The results showed reduced CMR in all conditions where the flanking and masking bands were temporally incoherent, in line with expectations of the temporal coherence hypothesis.