Binaural Masking Level Difference 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.

Dynamic Spatial Auditory Processing in the Elderly.

One of the most obvious functional effects of aging on the cognitive and processing processes of spatial hearing is the localization problem and the disorder of speech perception in noise. The purpose of the present study is to investigate the performance of dynamic spatial auditory processing in the elderly. This descriptive and analytical study was conducted on 60 young participants aged from18 to 25 years old and 60 elderly participants aged from 60 to 75 old years, using speech, spatial, and qualities of hearing scale (SSQ) questionnaire, binaural masking level difference (BMLD) and dynamic quick speech in noise (DS-QSIN) tests. Comparing the average scores of the tests and the questionnaire using the independent t test showed a significant difference between the two groups (p < 0.001). It was also found that gender had no effect on the results (p > 0.05). Aging is accompanied by different structural and functional changes in the auditory central nervous system, which leads to a decrease in speech perception in challenging listening environments, as well as a decrease in sound localization abilities, due to the reduction of temporal and spectral information. This problem affects the determination of the source of sound and the spatial cognition of the elderly and leads to a disturbance in the awareness of the auditory environment. Therefore, auditory rehabilitation programs can cause the improvement of spatial auditory processing performance and improve speech perception in noise in the elderly.

A spatial digit task for assessing binaural function in individuals with hearing loss

Spatial hearing is crucial in occupational tasks, yet until 2019, US Army fitness-for-duty requirements only considered hearing thresholds in the better ear. The regulation change introduced the Military Operational Hearing Test (MOHT) for those with worse-ear thresholds exceeding 40 dB HL at 0.5 or 1 kHz, or 60 dB HL at 2 kHz. This led to the development of the Spatial Digit Test (SDT) to assess binaural function in individuals with poor hearing in one ear but sufficiently good hearing in the other ear to pass a speech-in-noise test. The SDT involves digit pairs presented with Interaural Time Delays (ITDs) of +/−800 μs. Two studies were conducted: a validation study with over 200 individuals, and a verification study with more than 130 undergoing MOHT exams. Results show that individuals with normal auditory thresholds perform very well on the SDT, with about 95% correctly identifying at least 8 digits and 75% correctly identifying all 10. In contrast, only about 50% of individuals with monaural losses who took the SDT as part of the MOHT identified 8 or more digits. Results of the SDT were correlated both with subjective hearing complaints and with the Binaural Masking Level Difference. In conclusion, the SDT proves valuable for identifying individuals struggling using ITD cues to segregate and localize simultaneously presented speech signals.

Age-Related Deficits in Binaural Hearing: Contribution of Peripheral and Central Effects.

Pure-tone audiograms often poorly predict elderly humans' ability to communicate in everyday complex acoustic scenes. Binaural processing is crucial for discriminating sound sources in such complex acoustic scenes. The compromised perception of communication signals presented above hearing threshold has been linked to both peripheral and central age-related changes in the auditory system. Investigating young and old Mongolian gerbils of both sexes, an established model for human hearing, we demonstrate age-related supra-threshold deficits in binaural hearing using behavioral, electrophysiological, anatomical, and imaging methods. Binaural processing ability was measured as the binaural masking level difference (BMLD), an established measure in human psychophysics. We tested gerbils behaviorally with "virtual headphones," recorded single-unit responses in the auditory midbrain and evaluated gross midbrain and cortical responses using positron emission tomography (PET) imaging. Furthermore, we obtained additional measures of auditory function based on auditory brainstem responses, auditory-nerve synapse counts, and evidence for central inhibitory processing revealed by PET. BMLD deteriorates already in middle-aged animals having normal audiometric thresholds and is even worse in old animals with hearing loss. The magnitude of auditory brainstem response measures related to auditory-nerve function and binaural processing in the auditory brainstem also deteriorate. Furthermore, central GABAergic inhibition is affected by age. Because the number of synapses in the apical turn of the inner ear was not reduced in middle-aged animals, we conclude that peripheral synaptopathy contributes little to binaural processing deficits. Exploratory analyses suggest increased hearing thresholds, altered binaural processing in the brainstem and changed central GABAergic inhibition as potential contributors.

Low-frequency limit for binaural timing cues

Sound localization uses both interaural time differences (ITDs) and interaural level differences (ILDs). The ITD cue has a high-frequency boundary at 1500 Hz but is assumed to be limited only by the lowest audible frequency. We tested whether there is a low-frequency boundary for the ITD cue. Nineteen young, normal-hearing subjects participated in four experiments, in which 500-ms, 70-phon pure tones with various binaural cues were presented as a function of frequency from 62.5 to 2000 Hzin octave steps. The 70-phon level assured that audibility did not confound performance. Experiment 1 served as a control, in which a 10-dB ILD cue produced ∼90% correct lateralization at all frequencies. Experiment 2 measured lateralization accuracy with a 90-degree ITD cue, Experiment 3 measured the just-noticeable-difference from a 0-degree ITD standard, while Experiment 4 measured the binaural masking level difference in white noise. As expected, the listeners could not use the timingcue to perform these binaural tasks at 2000 Hz; Surprisingly, they showed significantly poorer performance at 62.5 Hz than mid frequencies. The band-pass characteristic result suggested a low-frequency boundary for binaural timing cues. This low boundary is not due to audibility but likely physical or physiological processes in the ear.

Binaural masking level difference for pure tone signals

The binaural masking level difference (BMLD) is a psychoacoustic method to determine binaural interaction and central auditory processes. The BMLD is the difference in hearing thresholds in homophasic and antiphasic conditions. The duration, phase and frequency of the stimuli can affect the BMLD. The main aim of the study is to evaluate the BMLD for stimuli of different durations and frequencies which could also be used in future electrophysiological studies. To this end we developed a GUI to present different frequency signals of variable duration and determine the BMLD. Three different durations and five different frequencies are explored. The results of the study confirm that the hearing threshold for the antiphasic condition is lower than the hearing threshold for the homophasic condition and that differences are significant for signals of 18ms and 48ms duration. Future objective binaural processing studies will be based on 18ms and 48ms stimuli with the same frequencies as used in the current study.

Responses to dichotic tone-in-noise stimuli in the inferior colliculus.

Human listeners are more sensitive to tones embedded in diotic noise when the tones are out-of-phase at the two ears (N0Sπ) than when they are in-phase (N0S0). The difference between the tone-detection thresholds for these two conditions is referred to as the binaural masking level difference (BMLD) and reflects a benefit of binaural processing. Detection in the N0Sπ condition has been explained in modeling studies by changes in interaural correlation (IAC), but this model has only been directly tested physiologically for low frequencies. Here, the IAC-based hypothesis for binaural detection was examined across a wide range of frequencies and masker levels using recordings in the awake rabbit inferior colliculus (IC). IAC-based cues were strongly correlated with neural responses to N0Sπ stimuli. Additionally, average rate-based thresholds were calculated for both N0S0 and N0Sπ conditions. The rate-based neural BMLD at 500 Hz matched rabbit behavioral data, but the trend of neural BMLDs across frequency differed from that of humans.

Development of a Binaural Masking Level Differences Test Application Using Tonal and Speech Stimuli in Persian and Assessing its Test-Retest Reliability in Normal-Hearing Young People

Background and Aim: The masking level difference (MLD) test is a behavioral test that assesses binaural interactions and central auditory processing. This study aims to design a binaural MLD (BMLD) test application using tonal and Speech Stimuli in Persian.&#x0D; Methods: In the first stage, the BMLD test application was designed in MATLAB software. Then, the spondaic words were recorded and added to the sound processing panel of the application. In the next stage, the MLD of tonal and speech stimuli was measured on 20 subjects aged 18–25 years. To examine the test-retest reliability of the application, all steps were repeated after one week.&#x0D; Results: The MLD values for tonal and speech stimuli under the SoNo-SπNo condition were significantly different from those under the SoNo-SoNπ condition (p&lt;0.05). These values for tonal and speech stimuli were 10.50 and 6.12 dB under the SoNo- SπNo condition, and 6.85 and 4.43 under the SoNo- SoNπ condition. There was no significant difference in the MLD values between males and females. The intraclass correlation coefficient value for different phase conditions was more than 0.8, indicating the high reliability of the BMLD test application for tonal and speech stimuli in Persian (p&lt;0.05).&#x0D; Conclusion: The designed BMLD test application using tonal and speech stimuli in Persian has similar results compared to the conventional methods of MLD test for other languages, therefore, this application can be used in audiology clinics in Iran to perform the MLD test.&#x0D; Keywords: Release from masking; masking; binaural hearing; software

The electrophysiological masking level difference: effects of age and mediation of hearing and cognition

Objective Evaluate the conceptual framework that age effects on the electrophysiological binaural masking level difference (MLD) are partially mediated by age-related hearing loss and/or global cognitive function via mediation analysis. Design Participants underwent a series of audiometric tests. The MLD was measured via cortical auditory evoked potentials using a speech stimulus (/ɑ/) in speech-weighted background noise. We used mediation analyses to determine the total effect, natural direct effects, and natural indirect effects, which are displayed as regression coefficients ([95% CI]; p value). Study sample Twenty-eight individuals aged 19–87 years (mean [SD]: 53.3 [25.2]), recruited from the community. Results Older age had a significant total effect on the MLD (-0.69 [95% CI: −0.96, −0.45]; p < 0.01). Neither pure tone average (-0.11 [95% CI: −0.43, 0.24; p = 0.54] nor global cognitive function (-0.02 [95% CI: −0.13, 0.02]; p = 0.55) mediated the relationship of age and the MLD and effect sizes were small. Results were insensitive to use of alternative hearing measures or inclusion of interaction terms. Conclusions The electrophysiological MLD may be an age-sensitive measure of binaural temporal processing that is minimally affected by age-related hearing loss and global cognitive function.

Monaural and binaural phase sensitivity in school-age children with early-childhood otitis media

Objective Previous research has linked recurrent otitis media (OM) during early childhood to reduced binaural masking level differences (BMLDs) in school-age children. How this finding relates to monaural processing abilities and the individual otologic history has not been investigated systematically. The current study, therefore, addressed these issues. Design Sensitivity to monaural and binaural phase information was assessed using a common test paradigm. To evaluate the influence of the otologic history, overall OM duration, OM onset age, and the time since the last OM episode were considered in the analyses. Study sample Children aged 6–13 years with a history of recurrent OM (N = 42) or without any previous ear diseases (N = 20). Results Compared to the controls, the OM children showed smaller BMLDs (p < 0.05) whereas their monaural and binaural detection thresholds were comparable (p > 0.05). After controlling for age, the otologic history factors failed to predict the BMLDs of the OM children. Their monaural detection thresholds were correlated with the binaural detection thresholds (r = ∼0.5, p < 0.05) but not the BMLDs. Conclusions The current study suggests that early-childhood OM can impair binaural processing abilities in school-age children.

A notched-noise precursor affects both diotic and dichotic notched-noise masking

The present study investigates how diotic and dichotic masked thresholds, in a notched-noise masking paradigm, are affected by activation of the Medial OlivoCochlear (MOC) reflex. Thresholds were obtained for a 500-Hz pure tone diotic or a dichotic signal, S (S0 or Sπ respectively), in the presence of a simultaneous or forward diotic masker (bandpass noise with no notch or a 400-Hz notch). A diotic precursor sound (bandpass noise with a 400- or 800-Hz notch) was presented prior to the signal and masker to activate the MOC reflex. For simultaneous- and forward-masking conditions, the decrease in masked thresholds as a notch was introduced in the masker was larger for the diotic than for the dichotic condition. This resulted in a reduced binaural masking level difference (BMLD) for the masker with a notch. The precursor augmented these two effects. The results indicate that the effect of the precursor, eliciting the MOC reflex, is less pronounced when binaural cues are processed.

Deep learning of the binaural masking level difference

The binaural masking level difference (BMLD) is the improvement in the detection of a signal in noise observed for different interaural configurations. Durlach [J. Acoust. Sci. Am. 1206–1218 (1963)] derived equations that accurately predict much of the human BMLD psychophysical data. We trained a deep neural network to predict BMLDs, as calculated with Durlach's equations, based on waveforms of a 500 Hz signal in a white noise each presented from different locations. Crucially, the network was constrained via nodes configured to embody informative representations (Iten etal., 2018; arXiv:1807.10300). The deep neural network accurately predicted BMLDs for stimuli within a simulated azimuth and for stimuli with interaural time differences (ITDs) outside the range of a human head. Further, even though the model was not designed to imitate neural biophysics, we discovered that the dynamics of latent nodes bore similarities with published data on neural ITD tuning and rate-level responses to BMLD stimuli. The work demonstrates how advances in deep learning can be used to consolidate theoretical and experimental approaches to binaural detection.

Modeling Binaural Unmasking of Speech Using a Blind Binaural Processing Stage.

The equalization cancellation model is often used to predict the binaural masking level difference. Previously its application to speech in noise has required separate knowledge about the speech and noise signals to maximize the signal-to-noise ratio (SNR). Here, a novel, blind equalization cancellation model is introduced that can use the mixed signals. This approach does not require any assumptions about particular sound source directions. It uses different strategies for positive and negative SNRs, with the switching between the two steered by a blind decision stage utilizing modulation cues. The output of the model is a single-channel signal with enhanced SNR, which we analyzed using the speech intelligibility index to compare speech intelligibility predictions. In a first experiment, the model was tested on experimental data obtained in a scenario with spatially separated target and masker signals. Predicted speech recognition thresholds were in good agreement with measured speech recognition thresholds with a root mean square error less than 1 dB. A second experiment investigated signals at positive SNRs, which was achieved using time compressed and low-pass filtered speech. The results demonstrated that binaural unmasking of speech occurs at positive SNRs and that the modulation-based switching strategy can predict the experimental results.

Effects of aging on spatial hearing.

Aging has several effects on auditory processing with the most important effect known as speech perception impairment in noise. The aim of the present study was to investigate the effects of aging on spatial hearing using quick speech in noise (QSIN) and binaural masking level difference (BMLD) tests and speech, spatial, and qualities of hearing scale (SSQ) questionnaire. The study was carried out on 34 elderly people, aged 60-75years, with normal peripheral hearing and 34 young participants, aged 18-25years. Using SSQ questionnaire and QSIN and BMLD tests, the spatial auditory processing ability was compared between the two groups. Comparison of mean scores using independent t test showed that there was a significant difference in the mean scores of QSIN, BMLD tests and SSQ questionnaire between the two groups (p < 0.001). Sex was not found to have any effect on the results (p > 0.05). Structural and neurochemical changes that occur in different parts of the central nervous system by aging affect various aspects of spatial auditory processing, such as localization, the precedence effect, and speech perception in noise. Lower scores of older adults with normal hearing in SSQ questionnaire and behavioral tests, compared with younger participants, may be considered as their weak performance in spatial auditory processing. The results of the present study reconfirm the effects of aging on spatial auditory processing, such as localization and speech perception in noise.

Comparing musicians and non-musicians in signal-in-noise perception

Objectives: The objective is to compare musicians and non-musicians in signal-in-noise perception.Design: Participants underwent the following tests: (1) High-frequency (HF) audiometry, (2) QuickSIN (a test for speech perception in noise), and (3) Binaural Masking Level Difference (BMLD) test (a test that examines the hearing threshold of a low-frequency tone from noise masking when the phase of the signal or noise in one ear is reversed with respect to the phase of the signal or noise in the other ear, i.e. the difference in the threshold for detection of the tone in noise under the SπNo and SoNo conditions).Study sample: Thirty-four healthy young normal-hearing listeners including 17 musicians (M) and 17 non-musicians (NM).Results: There were no study group difference in HF audiometry and QuickSIN. The M group had a significantly better performance under the SoNo but not under the SπNo condition. As a result, the BMLD value (SoNo–SπNo) was significantly smaller in the M group than in the NM group.Conclusions: There is a musicians’ advantage in binaural tone-in-noise detection in the BMLD task under the SoNo condition, suggesting that long-term music training positively shapes the auditory system.

Physiological studies of binaural tone-in-noise detection in the inferior colliculus of awake rabbit

With identical noise maskers presented to both ears, human listeners have lower tone detection thresholds when the tone is presented out-of-phase between the ears (N0Sπ) rather than in-phase (N0S0). The threshold difference is called the binaural masking level difference (BMLD). Human listeners have BMLDs up to at least 4 kHz, but previous studies to understand neural mechanisms have only used low-frequency tones. Here, we recorded single-neuron responses from the inferior colliculus in awake rabbit to a wide range of overall noise levels and tone frequencies near the neuron’s characteristic frequency. Maskers were 1/3-octave gaussian noise centered at the tone frequency. Neural thresholds at each noise level were estimated from average-rate responses at signal-to-noise ratios of -12 to +8 dB based on receiver-operating-characteristic analysis. Neural thresholds were similar across noise levels and were pooled together for further analysis. BMLDs of all recorded neurons with measurable thresholds for both N0S0 and N0Sπ ranged up to +17 dB (i.e., a substantial masking release for the N0Sπ condition). Across the population of neurons tuned to different frequencies, the largest BMLDs at each frequency decreased with increasing frequency, consistent with human psychophysical studies, but with a more gradual slope.

Pure-tone thresholds and the binaural masking level difference

Although several studies have examined the relationship between high-frequency pure-tone thresholds and the 500-Hz binaural masking level difference (BMLD), the results have not always been consistent. In this study, a retrospective analysis was conducted on an existing dataset from over 3000 military service members that included both pure-tone thresholds measured as part of their annual hearing conservation testing and a 33-trial clinical test of the BMLD. There was only a slight dependence of the 500-Hz BMLD on high-frequency pure-tone thresholds. For listeners with elevated pure-tone thresholds, this dependence was in good agreement with the findings of Jerger et al. [Arch. Otolaryngol. 110, 290–296 (1984)] and slightly larger than that reported by Wilson and Weakley [J. Am. Acad. Audiol. 16, 367–382 (2005)]. For listeners with near-normal hearing, the dependence of the 500-Hz BMLD on the 4-kHz pure-tone threshold was substantially less than that reported by Bernstein and Trahiotis [J. Acoust. Soc. Am. 140, 3540–3548 (2016)]. A possible explanation might be the degree of training offered to the subjects and procedural differences between clinical and laboratory techniques. [The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or U.S. Government.]

Age-related differences in binaural masking level differences: behavioral and electrophysiological evidence.

The effects of aging and stimulus configuration on binaural masking level differences (BMLDs) were measured behaviorally and electrophysiologically, using the frequency-following response (FFR) to target brainstem/midbrain encoding. The tests were performed in 15 younger normal-hearing (<30 yr) and 15 older normal-hearing (>60 yr) participants. The stimuli consisted of a 500-Hz target tone embedded in a narrowband (50-Hz bandwidth) or wideband (1,500-Hz bandwidth) noise masker. The interaural phase conditions included NoSo (tone and noise presented interaurally in-phase), NoSπ (noise presented interaurally in-phase and tone presented out-of-phase), and NπSo (noise presented interaurally out-of-phase and tone presented in-phase) configurations. In the behavioral experiment, aging reduced the magnitude of the BMLD. The magnitude of the BMLD was smaller for the NoSo-NπSo threshold difference compared with the NoSo-NoSπ threshold difference, and it was also smaller in narrowband compared with wideband conditions, consistent with previous measurements. In the electrophysiology experiment, older participants had reduced FFR magnitudes and smaller differences between configurations. There were significant changes in FFR magnitude between the NoSo to NoSπ configurations but not between the NoSo to NπSo configurations. The age-related reduction in FFR magnitudes suggests a temporal processing deficit, but no correlation was found between FFR magnitudes and behavioral BMLDs. Therefore, independent mechanisms may be contributing to the behavioral and neural deficits. Specifically, older participants had higher behavioral thresholds than younger participants for the NoSπ and NπSo configurations but had equivalent thresholds for the NoSo configuration. However, FFR magnitudes were reduced in older participants across all configurations. NEW & NOTEWORTHY Behavioral and electrophysiological testing reveal an aging effect for stimuli presented in wideband and narrowband noise conditions, such that behavioral binaural masking level differences and subcortical spectral magnitudes are reduced in older compared with younger participants. These deficits in binaural processing may limit the older participant's ability to use spatial cues to understand speech in environments containing competing sound sources.

Cortical Correlates of Binaural Temporal Processing Deficits in Older Adults.

This study was designed to evaluate binaural temporal processing in young and older adults using a binaural masking level difference (BMLD) paradigm. Using behavioral and electrophysiological measures within the same listeners, a series of stimulus manipulations was used to evaluate the relative contribution of binaural temporal fine-structure and temporal envelope cues. We evaluated the hypotheses that age-related declines in the BMLD task would be more strongly associated with temporal fine-structure than envelope cues and that age-related declines in behavioral measures would be correlated with cortical auditory evoked potential (CAEP) measures. Thirty adults participated in the study, including 10 young normal-hearing, 10 older normal-hearing, and 10 older hearing-impaired adults with bilaterally symmetric, mild-to-moderate sensorineural hearing loss. Behavioral and CAEP thresholds were measured for diotic (So) and dichotic (Sπ) tonal signals presented in continuous diotic (No) narrowband noise (50-Hz wide) maskers. Temporal envelope cues were manipulated by using two different narrowband maskers; Gaussian noise (GN) with robust envelope fluctuations and low-noise noise (LNN) with minimal envelope fluctuations. The potential to use temporal fine-structure cues was controlled by varying the signal frequency (500 or 4000 Hz), thereby relying on the natural decline in phase-locking with increasing frequency. Behavioral and CAEP thresholds were similar across groups for diotic conditions, while the masking release in dichotic conditions was larger for younger than for older participants. Across all participants, BMLDs were larger for GN than LNN and for 500-Hz than for 4000-Hz conditions, where envelope and fine-structure cues were most salient, respectively. Specific age-related differences were demonstrated for 500-Hz dichotic conditions in GN and LNN, reflecting reduced binaural temporal fine-structure coding. No significant age effects were observed for 4000-Hz dichotic conditions, consistent with similar use of binaural temporal envelope cues across age in these conditions. For all groups, thresholds and derived BMLD values obtained using the behavioral and CAEP methods were strongly correlated, supporting the notion that CAEP measures may be useful as an objective index of age-related changes in binaural temporal processing. These results demonstrate an age-related decline in the processing of binaural temporal fine-structure cues with preserved temporal envelope coding that was similar with and without mild-to-moderate peripheral hearing loss. Such age-related changes can be reliably indexed by both behavioral and CAEP measures in young and older adults.

Effect of duration and gating of the signal on the binaural masking level difference for narrowband and broadband maskers

Thresholds were measured for a 250-Hz signal with an interaural phase difference of 0° (diotic) or 180° (dichotic), with signal durations of 12 and 60 ms (including 6-ms ramps) and 300 ms (including 6- or 50-ms ramps). The signal-centered diotic noise masker had a bandwidth of 20 or 200 Hz. For the 20-Hz wide masker, the binaural masking level difference (BMLD), i.e., threshold difference between diotic and dichotic signal, increased with signal duration and, for the 300-ms signal, the BMLD was larger with 50-ms rather than 6-ms ramps. These signal parameters hardly affected the BMLD for the 200-Hz wide masker.