Masking Level Difference Research Articles

Blind modeling of binaural unmasking of speech in stationary maskers

The equalization cancellation (EC) model predicts the binaural masking level difference by equalizing interaural differences in level and time and increasing the signal-to-noise ratio (SNR) using destructive and constructive interferences. The EC model has been successfully combined with the speech intelligibility index (SII) to predict binaural speech intelligibility. Here a blind EC model is introduced that relies solely on the mixture of speech and noise, replacing the unrealistic requirement of the separated clean speech and noise signals in previous versions. The model uses two parallel EC paths, which either maximize or minimize the EC output level in each frequency band. If SNR is negative, minimization improves the SNR by removing the interferer component from the mixed signal. If SNR is positive, maximization improves the SNR by enhancing the target component. Either the minimizing or maximizing path in each frequency band is selected blindly based on envelope frequency-selective amplitude modula...

Modelling the frequency dependency of binaural masking level difference and its role for binaural unmasking of speech in normal hearing and hearing impaired listeners

In binaural tone-in-noise detection experiments humans can achieve substantially lower thresholds if either noise or tone have interaural time or phase differences (ITDs / IPDs) compared to diotic presentation of tone and noise. This effect is named binaural masking level difference (BMLD) and was mainly investigated at 500 Hz. The results obtained in these experiments were used to fit binaural processing errors in the equalization-cancelation (EC) mechanism, which is an effective model of binaural processing. In this study, the frequency dependency of BMLDs is investigated for listeners with normal hearing and high frequency hearing loss. Binaural tone-in-noise detection experiments are conducted for tone frequencies of 250, 500, 750, 1000, 1500, and 2000 Hz, and ITDs of the noise up to 5 times the period of the tested frequency. Furthermore, diotic and dichotic speech reception thresholds for low pass filtered speech in noise are measured with the same listeners. The EC mechanism with processing errors ...

Contributions of Nat Durlach to the field of haptics: Research on tactual communication of speech and manual sensing of mechanical properties

As a sensory scientist, Nat’s earliest contributions were through his theoretical and experimental work in the area of binaural hearing. Early in his career, however, he demonstrated an interest in comparative sensory processing as evidenced by a study to determine if the masking-level difference observed in audition would be found for stimulation on the skin (it was). Nat’s interest in the sense of touch continued through his research concerned with the use of the tactual sense as a substitute for hearing in the communication of speech and language for individuals with profound hearing impairment. This research encompassed studies with experienced deaf-blind users of natural methods of tactual communication (to establish an “existence proof” for the information-bearing capacity of the tactual sense) as well as research on methods for encoding and displaying acoustic signals for presentation through tactile aids. In addition, Nat also spearheaded efforts concerned with the development of haptic displays for use in virtual environment and teleoperator systems. His research in this area was concerned with advancements in knowledge regarding manual sensing and manipulation through a set of basic psychophysical studies. In this talk, we will summarize some of Nat’s important contributions in both of these areas.

Implementation and evaluation of a Danish test battery for auditory processing disorder in children

Objective: This study presents a Danish test battery for auditory processing disorder (APD). The tests were evaluated as to normative cut-off values (pass-fail criteria) and their test–retest reliability. Design: The battery consists of four behavioural tests: the filtered words (FW) test, the dichotic digits (DD) test, the gap detection (GD) test and the binaural masking level difference (BMLD) test. The tests were evaluated through listening experiments on children with no known history of auditory problems. Study sample: The normative cut-off values were obtained from 158 children (75 boys and 83 girls, aged 6–16 years), whereas the test–retest reliability was obtained from 20 children (10 boys and 10 girls, aged 6–11 years). Results: For each of the four tests one to four different cut-off values were determined depending on whether the scores from the two ears and the different age groups could be pooled. For each of the four tests the test–retest reliability was found to be satisfactory. The test–retest reliability was highest for the FW and the DD test. Conclusions: A Danish APD test battery is now available for clinical use with normative data.

Masking Level Difference (MLD): Literature Review

Masking Level Difference (MLD): Literature Review

Neural Correlates of the Binaural Masking Level Difference in Human Frequency-Following Responses.

The binaural masking level difference (BMLD) is an auditory phenomenon where binaural tone-in-noise detection is improved when the phase of either signal or noise is inverted in one of the ears (SπNo or SoNπ, respectively), relative to detection when signal and noise are in identical phase at each ear (SoNo). Processing related to BMLDs and interaural time differences has been confirmed in the auditory brainstem of non-human mammals; in the human auditory brainstem, phase-locked neural responses elicited by BMLD stimuli have not been systematically examined across signal-to-noise ratio. Behavioral and physiological testing was performed in three binaural stimulus conditions: SoNo, SπNo, and SoNπ. BMLDs at 500Hz were obtained from 14 young, normal-hearing adults (ages 21-26). Physiological BMLDs used the frequency-following response (FFR), a scalp-recorded auditory evoked potential dependent on sustained phase-locked neural activity; FFR tone-in-noise detection thresholds were used to calculate physiological BMLDs. FFR BMLDs were significantly smaller (poorer) than behavioral BMLDs, and FFR BMLDs did not reflect a physiological release from masking, on average. Raw FFR amplitude showed substantial reductions in the SπNo condition relative to SoNo and SoNπ conditions, consistent with negative effects of phase summation from left and right ear FFRs. FFR amplitude differences between stimulus conditions (e.g., SoNo amplitude-SπNo amplitude) were significantly predictive of behavioral SπNo BMLDs; individuals with larger amplitude differences had larger (better) behavioral B MLDs and individuals with smaller amplitude differences had smaller (poorer) behavioral B MLDs. These data indicate a role for sustained phase-locked neural activity in BMLDs of humans and are the first to show predictive relationships between behavioral BMLDs and human brainstem responses.

Binaural Hearing Ability With Bilateral Bone Conduction Stimulation in Subjects With Normal Hearing: Implications for Bone Conduction Hearing Aids.

The purpose of this study is to evaluate binaural hearing ability in adults with normal hearing when bone conduction (BC) stimulation is bilaterally applied at the bone conduction hearing aid (BCHA) implant position as well as at the audiometric position on the mastoid. The results with BC stimulation are compared with bilateral air conduction (AC) stimulation through earphones. Binaural hearing ability is investigated with tests of spatial release from masking and binaural intelligibility level difference using sentence material, binaural masking level difference with tonal chirp stimulation, and precedence effect using noise stimulus. In all tests, results with bilateral BC stimulation at the BCHA position illustrate an ability to extract binaural cues similar to BC stimulation at the mastoid position. The binaural benefit is overall greater with AC stimulation than BC stimulation at both positions. The binaural benefit for BC stimulation at the mastoid and BCHA position is approximately half in terms of decibels compared with AC stimulation in the speech based tests (spatial release from masking and binaural intelligibility level difference). For binaural masking level difference, the binaural benefit for the two BC positions with chirp signal phase inversion is approximately twice the benefit with inverted phase of the noise. The precedence effect results with BC stimulation at the mastoid and BCHA position are similar for low frequency noise stimulation but differ with high-frequency noise stimulation. The results confirm that binaural hearing processing with bilateral BC stimulation at the mastoid position is also present at the BCHA implant position. This indicates the ability for binaural hearing in patients with good cochlear function when using bilateral BCHAs.

Performance of children with mild or moderate sensory hearing loss on central auditory tests

Hearing is fundamental to the development of successful language skills. Deficits in hearing acuity and auditory processing (AP) can profoundly obstruct effective communication. Our study aimed to evaluate the performance of children with mild and moderate sensory hearing loss (HL) on central AP tests. The study included 50 children: 10 children with normal hearing who were used as controls; 20 children with mild sensory HL; and 20 children with moderate sensory HL. Both male and female children were equally represented. All children underwent otoscopic examination, pure tone audiometry, tympanometry, and acoustic reflex measurements. Questionnaires on central AP disorders, dyslexia, and attention deficit hyperactivity disorder were answered by the parents. Screening tests for AP abilities [pitch pattern sequence test, speech perception in noise (SPIN) right SPIN, left SPIN, dichotic digit test] were conducted. All children were then examined with the full versions of the previous tests in addition to auditory fusion test − revised, masking level difference test, binaural fusion test, competing sentence test, and low pass-filtered test. Arabic-version dyslexia assessment was carried out for those who failed the tests. The study revealed that children with mild and moderate HL who failed the screening tests also failed the full version tests, and when tested by the Arabic-version dyslexia assessment test, dyslexia was found as a comorbid condition.

Binaural processing in adults with a history of traumatic brain injury

An auditory processing deficit is a perceptual issue affecting how the central auditory nervous system understands and makes use of auditory information. Auditory processing deficits are typically associated with the pediatric population; however, anecdotal clinical evidence and the recent focus on central auditory effects of traumatic brain injury (TBI) suggests that auditory processing deficits may be prevalent among adults with a history of TBI. Individuals with symptoms of an auditory processing deficit often score within the normal range on standard clinical assessments. The objectiveof the current study, therefore, was to target measures of binaural processing to identify and characterize auditory processing deficits among adults with a history of TBI. Two groups were recruited: adults with a history of TBI and a control group. Binaural processing was measured with: 1) the Revised Speech Perception in Noise test measured in soundfield; 2) dichotic word recognition without and with low-pass filtering measured in the free recall and directed recall conditions; 3) the 500-Hz masking level difference; and 4) the Listening in Spatialized Noise Sentences Test. Results suggest that individuals with a history of TBI have lower than normal binaural performance.

Preliminary Measurements of Binaural Masking-Level Difference When Using Hearing Aids for Sensorineural Hearing Loss

The Binaural Masking-Level Difference phenomenon occurs both in listeners with normal hearing and with sensorineural hearing loss (SNHL). Previous studies of BMLDs involving SNHL listeners used a 500- or 2000-Hz pure tone as the target signal, but the BMLD performance of SNHL listeners with stimulus amplified for other frequencies has not been reported previously. Therefore, this study aimed to measure the BMLD in SNHL listeners at various frequencies after amplification by hearing aids. Thirty subjects with mild to moderately severe SNHL participated in the experiments. The BMLDs were measured based on the detection threshold differences for pure tones of 125, 250, 500, 1000, and 2000 Hz in the presence of white noise when presented interaurally in phase (S0N0) and interaurally in antiphase (SπN0). The results show that when using white noise as a masker, the average detection thresholds for the target signals were significantly lower in the SπN0 condition compared to those in the S0N0 condition (p < 0.001). The SNHL subjects had mean BMLDs of 2.3, 4.8, 4.7, 4.2, and 3.7 dB at 125, 250, 500, 1000, and 2000 Hz, respectively. The results obtained in the present study provide preliminary support that SNHL listeners hear target signals easier in noisy environments when the signals are amplified by hearing aids and presented in antiphase.

A metric for predicting binaural speech intelligibility in stationary noise and competing speech maskers.

One criterion in the design of binaural sound scenes in audio production is the extent to which the intended speech message is correctly understood. Object-based audio broadcasting systems have permitted sound editors to gain more access to the metadata (e.g., intensity and location) of each sound source, providing better control over speech intelligibility. The current study describes and evaluates a binaural distortion-weighted glimpse proportion metric-BiDWGP-which is motivated by better-ear glimpsing and binaural masking level differences. BiDWGP predicts intelligibility from two alternative input forms: either binaural recordings or monophonic recordings from each sound source along with their locations. Two listening experiments were performed with stationary noise and competing speech, one in the presence of a single masker, the other with multiple maskers, for a variety of spatial configurations. Overall, BiDWGP with both input forms predicts listener keyword scores with correlations of 0.95 and 0.91 for single- and multi-masker conditions, respectively. When considering masker type separately, correlations rise to 0.95 and above for both types of maskers. Predictions using the two input forms are very similar, suggesting that BiDWGP can be applied to the design of sound scenes where only individual sound sources and their locations are available.

Short-term visual deprivation can enhance spatial release from masking

This research aims to study the effect of short-term visual deprivation on spatial release from masking, a major component of the cocktail party effect that allows people to detect an auditory target in noise. The Masking Level Difference (MLD) test was administered on healthy individuals over three sessions: before (I) and after 90min of visual deprivation (II), and after 90min of re-exposure to light (III). A non-deprived control group performed the same tests, but remained sighted between sessions I and II. The non-deprived control group displayed constant results across sessions. However, performance in the MLD test was improved following short-term visual deprivation and performance returned to pre-deprivation values after light re-exposure. This study finds that short-term visual deprivation transiently enhances the spatial release from masking. These data suggest the significant potential for enhancing a process involved in the cocktail party effect in normally developing individuals and adds to an emerging literature on the potential to enhance auditory ability after only a brief period of visual deprivation.

Bridging the chasm: Animal physiology and human psychophysics

A goal of animal auditory neuroscience is to understand how humans process and perceive sound. Encouragingly, hypotheses about brain function, generated from psychoacoustics, are sometimes confirmed by physiological experiments. A notable example is the Jeffress model of processing of interaural time differences. This has been largely supported by physiology and indeed we showed that neural activity in the midbrain and cortex, in response to Binaural Masking Level Difference stimuli, was entirely consistent with this cross-correlation model of binaural processing. However, such comparisons of physiology and psychophysics are often beset by caveats of species and anesthesia. This is one reason why the sharpness of human frequency tuning is still currently debated. In recent experiments, we have measured tuning behaviorally and by direct and indirect physiological methods, all in the same species. These different measures are in good agreement, supporting the notion that the cochlea determines perceptual fr...

Stereophonic channel decorrelation using a binaural masking model

Traditional methods often only use monaural masking models to decorrelate input signals for stereo acoustic echo cancellation. Whereas, it seems more reasonable to use binaural masking models for the following two reasons. First, stereo signals are heard by two ears rather than just one. Second, psychoacoustic researchers have already shown that there are obvious masking level differences between binaural masking models and monaural masking models. By studying binaural masking level difference models, we first introduce a simplified binaural masking model for stereo acoustic echo cancellation. Considering that the interaural time difference is dominant at low frequencies (⩽1.5 kHz) and the interaural level difference is a major cue at higher frequencies, we propose to use different signal decorrelation schemes at these two frequency bands. In the low-frequency band, a pitch-driven sinusoidal injection scheme is proposed to maintain the interaural time difference, where the amount of injection is determined by the proposed binaural masking model. In the high-frequency band, a modified sinusoidal phase modulation scheme is applied to make a trade-off between preserving the interaural level difference and decorrelating the stereophonic input signals. Assessment results show that the proposed method can effectively improve the non-unique problem and retain good speech quality.

Effect of musical training on masking paradigm

Background: Musicians outperform nonmusicians on brainstem and cortical level processing. However, there are limited literature comparing musicians and nonmusicians on the overall release of masking abilities and correlation across otoacoustic emissions (OAEs), masking level difference (MLD) and quick speech-in-noise (Quick-SIN). Aim: To investigate the physiological differences between musicians and nonmusicians by evaluating the effect of musical training on contralateral suppression (CAS) of OAE, MLD, and Quick-SIN. Materials and Methods: Distortion product OAEs (DPOAEs) recording with and without noise, MLD test using continuous (CMLD) and pulsating pure tones (PMLD) and Quick-SIN in Kannada were carried out on 15 musicians and 15 nonmusicians. Results: Musicians outperformed nonmusicians on Quick-SIN and CAS of OAEs. However, no significant difference was observed between two groups on CMLD and PMLD. There was a significant difference observed in CMLD, PMLD as well as suppression amplitude across frequencies tested in both groups. A significant difference between PMLD and CMLD was observed only for musicians at 2 kHz. In both groups, there was a significant level of correlation for CAS of DPOAE and Quick-SIN with CMLD and with PMLD between the parameters tested. Conclusion: The results of our finding suggest that CAS of DPOAE and Quick-SIN are sensitive tools to quantify the effect of musical training, compared to MLD. Musical training helps to strengthen afferent and efferent pathways, and hence it aids in speech perception abilities in noise. Hence, for the intervention of individuals with difficulties in speech perception in noise, musical training can be a choice to be considered. As well for appropriate diagnosis and interpretation, one needs to consider the musical experience of individual tested.

Intelligibility for Binaural Speech with Discarded Low-SNR Speech Components.

Speech intelligibility in multitalker settings improves when the target speaker is spatially separated from the interfering speakers. A factor that may contribute to this improvement is the improved detectability of target-speech components due to binaural interaction in analogy to the Binaural Masking Level Difference (BMLD). This would allow listeners to hear target speech components within specific time-frequency intervals that have a negative SNR, similar to the improvement in the detectability of a tone in noise when these contain disparate interaural difference cues. To investigate whether these negative-SNR target-speech components indeed contribute to speech intelligibility, a stimulus manipulation was performed where all target components were removed when local SNRs were smaller than a certain criterion value. It can be expected that for sufficiently high criterion values target speech components will be removed that do contribute to speech intelligibility. For spatially separated speakers, assuming that a BMLD-like detection advantage contributes to intelligibility, degradation in intelligibility is expected already at criterion values below 0 dB SNR. However, for collocated speakers it is expected that higher criterion values can be applied without impairing speech intelligibility. Results show that degradation of intelligibility for separated speakers is only seen for criterion values of 0 dB and above, indicating a negligible contribution of a BMLD-like detection advantage in multitalker settings. These results show that the spatial benefit is related to a spatial separation of speech components at positive local SNRs rather than to a BMLD-like detection improvement for speech components at negative local SNRs.

Effects of Age and Hearing Loss on the Processing of Auditory Temporal Fine Structure.

Within the cochlea, broadband sounds like speech and music are filtered into a series of narrowband signals, each of which can be considered as a relatively slowly varying envelope (ENV) imposed on a rapidly oscillating carrier (the temporal fine structure, TFS). Information about ENV and TFS is conveyed in the timing and short-term rate of nerve spikes in the auditory nerve. There is evidence that both hearing loss and increasing age adversely affect the ability to use TFS information, but in many studies the effects of hearing loss and age have been confounded. This paper summarises evidence from studies that allow some separation of the effects of hearing loss and age. The results suggest that the monaural processing of TFS information, which is important for the perception of pitch and for segregating speech from background sounds, is adversely affected by both hearing loss and increasing age, the former being more important. The monaural processing of ENV information is hardly affected by hearing loss or by increasing age. The binaural processing of TFS information, which is important for sound localisation and the binaural masking level difference, is also adversely affected by both hearing loss and increasing age, but here the latter seems more important. The deterioration of binaural TFS processing with increasing age appears to start relatively early in life. The binaural processing of ENV information also deteriorates somewhat with increasing age. The reduced binaural processing abilities found for older/hearing-impaired listeners may partially account for the difficulties that such listeners experience in situations where the target speech and interfering sounds come from different directions in space, as is common in everyday life.

Relação entre os achados do teste masking level difference e do reflexo acústico em crianças com transtorno fonológico

Resumo: OBJETIVO: investigar os achados do teste Masking Level Difference com os resultados do reflexo acústico e a composição do sistema fonológico de crianças com transtorno fonológico, com o propósito de verificar se há associações que possam auxiliar a compreensão do processo de aquisição de linguagem atípica. MÉTODOS: estudo quantitativo, observacional e descritivo, desenvolvido por meio de levantamento secundário de um banco de dados, constituído de avaliações fonoaudiológicas de 110 crianças com transtorno fonológico, com idades entre 5 e 10 anos. Para a composição do corpus deste estudo o requisito utilizado foi a realização da timpanometria, com curva timpanométrica do tipo A (Jerger) e possuir avaliação do Masking Level Difference. RESULTADOS: dos dados de 110 crianças, 57 se enquadraram nestes requisitos, compondo a população deste estudo, sendo 42 do sexo masculino e 15 do sexo feminino. Destas 57 crianças, 23 (40,3%) apresentam resultado do Masking Level Difference normal e 34 (59,7%) apresentam resultado alterado. Não foi encontrada diferença estatística na relação entre o Masking Level Difference com as variáveis idade, sexo, grau de inteligibilidade de fala e o resultado do reflexo acústico contralateral e ipsilateral. Na relação entre a aquisição fonológica dos fonemas em onsetinicial e medial, foi encontrada significância estatística entre a não aquisição dos fonemas /s/ e /ʀ/ em onset inicial e /s/ e /z/ em onset medial com o resultado do teste alterado. CONCLUSÃO: outras habilidades do processamento auditivo, além da interação binaural, devem ser estudadas a fim de identificar a relação deste com o transtorno fonológico.

The Impact of Auditory Processing and Cognitive Abilities in Children.

To examine the links between auditory processing (AP) test results, functional deficits, and cognitive abilities. One hundred and fifty-five children, ages 7-12 years, comprising 50 control children and 105 children referred for AP assessment, all with normal peripheral hearing, completed an AP and cognitive (sustained attention, auditory working memory, and nonverbal intelligence) test battery. Functional outcome measures of listening ability (developed using questionnaires from parent, teacher, and child respondents) and reading fluency were also collected. AP scores for dichotic digits, frequency pattern, and listening in spatialized noise-sentences test baseline scores showed significant intertask correlations, and significant correlations with functional outcomes. The gaps in noise task showed correlation with reading fluency only. The AP tasks of masking level differences and spatial advantage showed no correlation with listening ability or reading fluency. Results showed significantly poorer cognitive abilities overall in the children referred for AP assessment compared with the control group. Within the referred group, children diagnosed with an auditory processing disorder had significantly poorer cognitive abilities than those passing the test battery. Correlation and regression studies showed significant associations between AP and cognitive scores. The results of multilinear regression analyses showed that the associations of AP scores with listening and academic results were no longer significant when cognitive scores were also included as predictors. A complex interaction of cognitive abilities and AP scores is evident. For many children with listening difficulties, who perform poorly on AP tasks, cognitive deficits are also in place. Although the direction of causality is unclear, it is likely that these cognitive deficits are causing the perceived difficulty and/or are having a significant effect on the test results. Interpretation of AP tests requires consideration of how cognitive abilities may have impacted on not only task results but also the functional difficulties experienced by the child.

How to Quantify Binaural Hearing in Patients with Unilateral Hearing Using Hearing Implants

Application of bilateral hearing devices in bilateral hearing loss and unilateral application in unilateral hearing loss (second ear with normal hearing) does not a priori lead to binaural hearing. An overview is presented on several measures of binaural benefits that have been used in patients with unilateral or bilateral deafness using one or two cochlear implants, respectively, and in patients with unilateral or bilateral conductive/mixed hearing loss using one or two percutaneous bone conduction implants (BCDs), respectively. Overall, according to this overview, the most significant and sensitive measure is the benefit in directional hearing. Measures using speech (viz. binaural summation, binaural squelch or use of the head shadow effect) showed minor benefits, except for patients with bilateral conductive/mixed hearing loss using two BCDs. Although less feasible in daily practise, the binaural masking level difference test seems to be a promising option in the assessment of binaural function.