Binaural Fusion Research Articles

Contrastive adaptation effects along a voice-nonvoice continuum.

Adaptation to the environment is a universal property of perception across all sensory modalities. It can enhance the salience of new events in an ongoing background and helps maintain perceptual constancy in the face of variable sensory input. Several contrastive adaptation effects have been identified using sounds within the categories of human voice and musical instruments. The present study investigated whether such contrast effects can occur between voice and nonvoice stimulus categories. A 10-step continuum between "voice" (/a/, /o/, or /u/ vowels) and "instrument" (bassoon, horn, or viola) sounds was generated for each of the nine possible pairs. In each trial, an adaptor, either a voice or instrument, was played four times and was followed by a target from along the appropriate continuum. When trials with voice and instrumental adaptors were grouped into separate blocks, strong contrastive adaptation effects were observed, with the target more likely to be identified as a voice following instrumental adaptors and vice versa (Experiment 1). The effects were not observed for visual image adaptors (Experiment 2). The effects were somewhat larger when the adaptors and the target were presented to the same than to different ears, but significant adaptation was observed in both conditions, suggesting contributions of central mechanisms, following binaural integration (Experiment 3). The effect accumulated when the same type of adaptor was presented consecutively and persisted following the end of the adaptors (Experiment 4). The discovery of voice-nonvoice contrastive pairs opens the possibility of studying perceptual or neuronal voice selectivity while keeping acoustic features constant. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Auditory processing abilities of children with congenital blindness

BackgroundChildren with visual challenges rely on their hearing ability to accomplish daily tasks more efficiently. Many investigations show changes in the auditory pathway in children and adults with early blindness. It can be hypothesized that the auditory processing abilities of children with congenital blindness will be superior to those of typically developing children without any visual challenges. PurposeThe current study was designed to compare some of the auditory processing abilities of children with congenital blindness and typically developing children who do not have any visual challenges. Specifically, the study compared the perception of speech in noise, temporal patterning ability, binaural integration ability as well as auditory memory and sequencing abilities of children in two groups. Research designIt was a prospective cross-sectional study comparing two groups. Study sampleA total of 160 children, 80 typically developing children without any visual challenges (reference group) and 80 children with congenital blindness, in the age range of 7–11 years, participated in the study. Data collection and analysisPitch pattern test (PPT), perception of speech perception in noise test in Marathi (PSIN-M), dichotic digit test in Marathi (DDT-M), and auditory memory and sequencing test in Marathi (AMST-M) were administered. Independent sample T test and Mann Whitney U test were used to compare the performance of the two groups on these tests. ResultsChildren with congenital blindness showed significantly better scores on PPT, PSIN-M, and DDT-M as compared to children in the reference group in all the age groups. A clear trend was not observed on DDT-M. ConclusionIt can be concluded that children with congenital blindness have better auditory processing, auditory memory, and sequencing abilities compared to typically developing children without any visual challenges.

Binaural fusion: Complexities in definition and measurement.

Despite the growing interest in studying binaural fusion, there is little consensus over its definition or how it is best measured. This review seeks to describe the complexities of binaural fusion, highlight measurement challenges, provide guidelines for rigorous perceptual measurements, and provide a working definition that encompasses this information. First, it is argued that binaural fusion may be multidimensional and might occur in one domain but not others, such as fusion in the spatial but not the spectral domain or vice versa. Second, binaural fusion may occur on a continuous scale rather than on a binary one. Third, binaural fusion responses are highly idiosyncratic, which could be a result of methodology, such as the specific experimental instructions, suggesting a need to explicitly report the instructions given. Fourth, it is possible that direct ("Did you hear one sound or two?") and indirect ("Where did the sound come from?" or "What was the pitch of the sound?") measurements of fusion will produce different results. In conclusion, explicit consideration of these attributes and reporting of methodology are needed for rigorous interpretation and comparison across studies and listener populations.

Impact of an Auditory Processing Training Program on Individuals With Autism Spectrum Disorder.

Children and young adults diagnosed with autism spectrum disorder (ASD) often report and exhibit significant auditory processing difficulties, particularly in background noise. This study extends our previous work by examining the potential benefits of a 12-week auditory processing training (APT) program designed to address the auditory processing difficulties in individuals with ASD via auditory training and the use of remote-microphone technology. Effect sizes of training benefits also were calculated, and principal component analysis (PCA) was used to consolidate performance across various tests into fewer meaningful constructs related to auditory processing in this population. Twenty-eight children and young adults with ASD participated in a 12-week APT program that included one-on-one speech-in-noise training, computerized dichotic training, and use of remote-microphone technology at home and at school. Before and after training, each participant completed tests of speech recognition in noise, spatial processing, binaural integration, and general auditory processing skills. Significant performance improvements and medium-to-large effect sizes were found across most test measures after the participants completed the APT program and when using the remote-microphone system. PCA identified strong relationships among all test measures as well as documented the relationships between behavioral performance, training duration, and training improvements. The APT program significantly improved spatial processing, binaural integration, phonological processing, auditory memory, auditory cohesion, and speech recognition in noise in individuals with ASD when the remote-microphone system was used. PCA analysis of pre- and posttraining data showed a strong relationship among all test measures, suggesting an abbreviated auditory processing test battery may be feasible for individuals with ASD. Training duration (minutes) and training improvements were associated with performance outcomes measured by the test battery.

Perceived Trajectories of Cyclic Sound Movement

Binaural beats are a phenomenon that occurs during dichotic stimulation due to binaural integration. It takes the form of cyclic movement of the sound image in the listener’s acoustic space when the beat frequency range is below 3 Hz. Our subjects used the inserted earphones to listen to the stimuli that created a sense of sound movement due to changes in the interaural time difference (ITD). We used three types of dichotic stimuli which simulated smooth azimuthal cyclic movement and cyclic abrupt shifts. The ITD changes determined central or lateral positions of movement trajectories. The results confirm that both types of movement created the effect of binaural beats. The range of beats depended on the spatial position of the trajectory: in the frontal sector of acoustic space, the range of beats was greater than on the left or right. The perceived trajectories of smooth motion were shorter than the trajectories of abrupt shift. The influence of spatial position on the perceived trajectory length is interpreted from the standpoint of nonlinear features of lateralization. It is suggested that the effect of ITD pattern on the perceived trajectory length is mediated by temporal integration mechanisms of binaural hearing.

Assessing Binaural Auditory Processing in Native Tamil Speaking Children.

The objective of this study is to develop and validate the Binaural Fusion Test (BFT) in the Tamil language for children with learning disability. As many children with learning disability exhibit an auditory processing deficit there is a need for language specific assessment tool for these children. The BFT in Tamil comprises 100 words organized into four lists, with each list containing 25 words. A total of 84 children with normal auditory processing and 45 children diagnosed with learning difficulties were administrated the BFT in Tamil. Test-retest reliability was evaluated in a sample of 30 children who exhibited normal auditory processing. The results of BFT in children with normal auditory processing demonstrated satisfactory reliability by the Cronbach Alpha test. A statistically significant difference was seen in the mean scores of BFT in Tamil when comparing the groups. The present study offers novel normative data for the binaural fusion test in Tamil, which has not been previously documented in the existing literature. For children, the BFT in Tamil, which is a part of the CAPD test battery, can be used to find binaural interaction deficiencies.

The Relationship Between Auditory and Cognitive Processing Abilities in Children With Specific Learning Disorders.

Specific learning disorder (SLD) refers to a pattern of learning difficulties characterized by problems with reading, writing, or mathematics that are not solely due to intellectual disabilities, sensory deficits, or other neurological or medical conditions. It is a neurodevelopmental disorder that affects the processing and organizing of information. Auditory and cognitive processing is affected in most children with SLD, although to a varying degree. However, it is still unclear whether there exists any relationship between auditory and cognitive processing disorders in children with SLD. We tested 1,259 children, of whom 77 were diagnosed as SLD and 30 age- and gender-matched typically developing (TD) children were selected. Auditory processing abilities were assessed for auditory discrimination, pattern perception, closure, temporal processing, binaural integration, and separation using standardized tests and procedures. Cognitive processing was measured using working memory, short-term memory, and attention tasks. The test data of the TD children were taken as the norm. Based on the normative range, children with SLD were divided into those with auditory processing disorder (APD; n = 31) and those without APD (n = 46). A regression model highlighted a robust positive relationship between APD and cognitive processing, particularly pronounced in SLD with APD children. The results are discussed, supporting the information-processing theory of learning disability and highlighting a complex loop between auditory and cognitive deficits in children with SLD. The findings underscore the critical role of both auditory and cognitive abilities in children with SLD. Tailoring the intervention to break the loop is recommended, which may improve learning abilities more effectively.

Development and Evaluation of the Italian Version of the Dichotic Digit Test: Insights from 39 Normal-Hearing Children Aged 11 to 13 years.

BACKGROUND The dichotic digit test (DDT) is one of the tests for the behavioral assessment of central auditory processing. Dichotic listening tests are sensitive ways of assessing cortical structures, the corpus callossum, and binaural integration mechanisms, showing strong correlations with learning difficulties. The DDT is presently available in a number of languages, each appropriate for the subject's native language. However, there is presently no test in the Italian language. The goal of this study was to develop an Italian version of the one-pair dichotic digit test (DDT-IT) and analyze results in 39 normal-hearing Italian children 11 to 13 years old. We used 2 conditions of presentation: free recall and directed attention (left or right ear), and looked at possible effects of sex and ear side. MATERIAL AND METHODS This study involved 3 steps: creation of the stimuli, checking their quality with Italian speakers, and assessment of the DDT-IT in our subject pool. The study involved 39 children (26 girls and 13 boys), aged 11-13 years. All participants underwent basic audiological assessment, auditory brainstem response, and then DDT-IT. RESULTS Results under free recall and directed attention conditions were similar for right and left ears, and there were no sex or age effects. CONCLUSIONS The Italian version of DDT (DDT-IT) has been developed and its performance on 39 normal-hearing Italian children was assessed. We found there were no age or sex effects for either the free recall condition or the directed attention condition.

Predictive factors for broad binaural pitch fusion in adults with hearing aids and cochlear implants

Many adults with hearing loss who use hearing aids (HAs) and/or cochlear implants (CIs) have broad binaural pitch fusion, such that sounds with large pitch differences are fused across ears, leading to difficulties separating voices in multi-talker environments. However, there is individual variation. The goal of the current study was to investigate whether auditory experience factors explain this variation in broad binaural fusion. Binaural fusion was measured in adults with various hearing device combinations: 26 bilateral HA, 25 bimodal CI, and 27 bilateral CI users. Fusion ranges were measured by simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus to find the range that fused with the reference stimulus. Factors examined included age at testing, degree of HL, amount of amplification, age of onset of HL, duration of HL without CI, and duration of HA, bimodal CI, and bilateral CI use. Preliminary analyses suggest that broad fusion is correlated with long durations of HA use; further analyses using multivariable models will be described. The findings will indicate how hearing device experience may influence binaural pitch fusion. [Work supported by NIH grant R01 DC013307.]

Binaural fusion and vowel perception in cochlear implant users

Excess binaural fusion can be a problem, especially in noisy environments when speech from multiple talkers are fused together. Previously, we showed that hearing aid users experience abnormally broad binaural fusion that leads to fusion and averaging of dichotic vowels of fundamental frequency (F0) differing by up to 1 octave (Reiss and Molis 2021). This study investigated whether cochlear implant (CI) listeners also experience abnormal fusion and averaging of double vowels in the free field. Six adult CI users (4 females) and four NH adults (1 female) were tested. Stimuli were synthetic vowels/æ/, /a/, /u/ and /i/, at F0 = 106.9, 151.2, and 201.8 Hz. Two different vowels were presented simultaneously from two loudspeakers at ±60°, with same or different F0. Subjects were instructed to select which one or two vowels they perceived. When ΔF0 = 0, NH and CI users often fused and identified only one vowel. As ΔF0 increased, NH listeners increased identification of two vowels, while CI users continued to fuse vowels. The findings show that in realistic free field listening conditions, CI users can experience excess fusion of multiple vowels of differing F0s, presenting additional challenges in noisy listening environments. [Work supported by NIH R01DC013307 and ASA SUREIA program.]

Processamento auditivo central e afasia: uma revisão de escopo

ABSTRACT Purpose: to report scientific evidence on the impact of aphasia on central auditory processing and map the contribution of auditory training to aphasic individuals. Methods: a scoping review approaching national and international databases (SciELO, LILACS, PubMed, Scopus, and Cochrane Library) and the gray literature (Google Scholar and Open Grey). The inclusion criteria covered articles that addressed the interface between central auditory processing and aphasia, excluding duplicates, literature reviews, and scientific abstracts. Literature Review: the review comprised 13 articles that met the eligibility criteria for this study. Seven of the selected articles assessed central auditory processing, four used electrophysiological examinations (such as auditory brainstem response and long-latency auditory evoked potentials) to assess the auditory pathway, and only one analyzed the intervention in aphasic individuals with auditory training. Conclusion: scientific evidence points to an important change in aphasic people’s central auditory processing, with impaired figure-ground, auditory closure, temporal resolution and ordering, and binaural integration. Moreover, it is relevant to assess auditory processing, given the contribution of auditory training in speech-language-hearing therapy for a better prognosis in the rehabilitation of aphasia.

Cognitive Auditory Training: Comparative Impact of Telerehabilitation and In-person Training

Abstract Background: Cognitive auditory approach has been shown effective in assessment and intervention with children with Central Auditory Processing Disorders (CAPD). Objective: To compare the intervention methods: telerehabilitation for synchronous auditory training through an Online Cognitive Auditory Training Program, with the traditional rehabilitation method, called acoustically controlled auditory training, carried out in person in an acoustic booth. Methods: The sample included 23 children between the ages of 7 and 9, of both genders, living in the state of São Paulo, Brazil, who were divided into two groups: Group I - 13 children undergoing telerehabilitation and Group II - 10 children undergoing auditory training in an acoustic booth. The instruments used were: i) Pediatric Speech Intelligibility (PSI) test in the ipsilateral competitive messages (ICM condition); ii) Digit Dichotic (DD) in binaural integration and separation skills test in auditory separation and integration skills. Results: In this study the following results were: a) there were statistically significant differences in the performance of children who underwent telerehabilitation for CAPD, revealing the reliability of the method, b) there were statistically significant differences both in the effect of auditory training carried out through telerehabilitation and in the effect of auditory training carried out in person, proving that the effectiveness of the two methods is equivalent, c) there were statistically significant differences in the performance of school-age students with CAPD who used the Online Cognitive Auditory Training Program, showing that the cognitive auditory approach is effective in intervention with children with CAPD. Conclusion: There is efficacy in cognitive auditory training through the telerehabilitation intervention. Results shown that intervention through the Online Cognitive Auditory Training Program support student learning and communication skills. Keywords: Auditory Processing, Cognitive Auditory Training, Telerehabilitation, Central Auditory Processing Disorders (CAPD).

Comparing the influence of auditory streaming cues on binaural pitch fusion in normal-hearing and hearing-impaired listeners

Binaural pitch fusion occurs when dichotic signals eliciting a different pitch are perceived as one sound. Previously, we investigated the effects of auditory streaming cues on binaural fusion using a modification of the ABA streaming paradigm. A dichotic stimulus (fixed tone at frequency fref in the reference ear and variable frequency in the contralateral ear) was presented at alternating intervals with up to 3 “capture” tones at fref. Participants reported whether they perceived galloping or two streams. Binaural fusion frequency range decreased with the number of capture tones and longer inter-stimulus intervals (ISIs), suggesting competition of sequential grouping with capture tones versus simultaneous grouping (fusion) with the dichotic tone. In the present study, we compared the effects in NH and hearing-impaired (HI) listeners. Preliminary data from 13 NH and 5 HI listeners suggest greater reductions in fusion range with number of capture tones and with longer ISI in HI listeners, especially in listeners with broad binaural fusion. These findings indicate that auditory grouping cues can reduce binaural fusion in both NH and HI listeners. Funded by NIH/NIDCD R01DC013307.

Binaural fusion with ecologically valid stimuli

Binaural fusion, or the perception of a single auditory “image” can arise from simultaneous inputs across ears. Fusion is fundamental to binaural abilities, including sound source localization. One potent determiner of degree of fusion is the interaural correlation of the binaurally presented waveforms. Noise waveforms can be used to manipulate the interaural correlation, but the normalized correlation of the envelopes of such noises is limited to between 1.0 and 0.785 (π/4). As a result of differing properties between noises and speech, pairs of speech sounds can be generated having normalized interaural envelope correlations well below 0.785. We measured cochlear implant users’ perceived degree of binaural fusion while varying the interaural correlation of speech-like signals from 0.4 to 1.0. Stimuli were generated using speech-based envelopes from multi-channel vocoders that modulated 1000 pulse-per-second pulse trains. Envelopes derived from different vocoder channels were extracted to yield interaural correlations that varied over a wider range than would be possible using noises. Preliminary results suggest that the speech-based stimuli, while differing qualitatively from noises and being more ecologically valid, yield similar effects of interaural correlation on binaural fusion, while allowing a larger range of interaural correlations to be employed.

Does sensitivity to interaural correlation changes correlate with binaural fusion performance?

The purpose of this study was to assess whether and to what degree sensitivity to changes in interaural correlation (IC) in bilateral cochlear implant (CI) listeners is related to the overall degree of binaural fusion those listeners experience. Compared to typical-hearing listeners, CI users often report perceiving a reduced degree of binaural fusion. Because IC is a strong determiner of perceived fusion, degraded perception of fusion might be coupled with a relative insensitivity to changes in IC. To investigate this, two experiments were conducted. First, discrimination of IC changes was measured using the method of constant stimuli in which CI listeners identified the “target” interval containing an IC differing from the “reference” values of either 0.7 or 1.0. Stimuli were generated by modulating 1-kHz pulse trains by speech-derived envelopes the IC of which were manipulated. The same stimuli were used in a second procedure in which the perceived degree of fusion was quantified for ICs varying between 0.4–1.0. Preliminary results from both studies suggest that relative insensitivity to changes in IC are associated with a lesser degree of perceived fusion, overall.

Investigating the effect of cochleotopic region on temporal processing using binaural fusion

Processing of temporal information in a signal may vary across apical, mid and basal regions of the cochlea—there is evidence for this in both cochlear-implant and typical-hearing listeners. This effect may also be task dependent and has not been studied with respect to binaural fusion. Fusion depends on tracking the temporal fluctuations across ears which can be manipulated by varying the interaural correlation (IC) of a signal. To investigate the effect of place of stimulation on fusion, 9 bilateral cochlear implant users were presented with 1000 Hz pulse trains with varying envelope IC. An apical, mid, and basal electrode were separately selected as reference, each of which was then paired with five electrodes in the contralateral ear, spread across the array. Listeners indicated the spatial diffuseness and the number of auditory “images” of the perceived sound by manipulating a visual representation of their perception superimposed on a picture of a head. Preliminary results indicate that, for optimally paired electrodes, fusion increases similarly for the three regions of the cochlea with increasing IC, and when IC is 1, the degree of fusion is comparable across regions. Processing of temporal information for binaural fusion is not significantly different across cochleotopic regions.

A Survey on Screening and Diagnostic Criteria of Auditory Processing Disorders in India.

The current study aimed to determine the criteria used for screening and diagnosing cases with central auditory processing disorders (CAPD) in India. A cross-sectional questionnaire-based survey design was used in the present study. A questionnaire was developed to determine the criteria used for screening and diagnosing CAPD across clinics in India. Responses were obtained from 83 participants from all over India. Results indicated that 78% of respondents were currently doing CAPD evaluation. In that, the majority of respondents (63%) had a predetermined minimum battery that was relatively adaptable depending on the case history and age of the patient. In screening, most respondents used a screening questionnaire (SCAP, 75%) and a screening test (STAP, 60%). In the diagnostic protocol, the most used tests by the respondents were masking level difference (MLD), repetition of words (RW), gap detection test (GDT), pitch pattern test (PPT), speech perception in noise (SPIN), digit span test (DST), dichotic digit test (DDT), binaural fusion test (BFT), auditory brainstem response (ABR), dichotic CV test (DCVT), and duration pattern test (DPT). The current study's result will help professionals choose the minimum test battery for diagnosing CAPD.

Duplex perception reveals brainstem auditory representations are modulated by listeners' ongoing percept for speech.

So-called duplex speech stimuli with perceptually ambiguous spectral cues to one ear and isolated low- versus high-frequency third formant "chirp" to the opposite ear yield a coherent percept supporting their phonetic categorization. Critically, such dichotic sounds are only perceived categorically upon binaural integration. Here, we used frequency-following responses (FFRs), scalp-recorded potentials reflecting phase-locked subcortical activity, to investigate brainstem responses to fused speech percepts and to determine whether FFRs reflect binaurally integrated category-level representations. We recorded FFRs to diotic and dichotic stop-consonants (/da/, /ga/) that either did or did not require binaural fusion to properly label along with perceptually ambiguous sounds without clear phonetic identity. Behaviorally, listeners showed clear categorization of dichotic speech tokens confirming they were heard with a fused, phonetic percept. Neurally, we found FFRs were stronger for categorically perceived speech relative to category-ambiguous tokens but also differentiated phonetic categories for both diotically and dichotically presented speech sounds. Correlations between neural and behavioral data further showed FFR latency predicted the degree to which listeners labeled tokens as "da" versus "ga." The presence of binaurally integrated, category-level information in FFRs suggests human brainstem processing reflects a surprisingly abstract level of the speech code typically circumscribed to much later cortical processing.

Differential advantages of musical backgrounds on binaural integration and interaction skills in instrumentalists, vocalists, and non-musicians

BackgroundMusical perception requires a host of skills. Instrumental musicians place greater emphasis on motor coordination, whereas vocal musicians rehearse vocal sounds. The study explored the differential advantages of musical background on binaural integration and interaction in musicians (instrumentalists, vocalists) and compared them with age-matched non-musicians. MethodsEight six participants aged 20–40 y with normal hearing sensitivity were subjected to binaural tests using a standard group comparison research design. The participants were segregated into three groups – Group 1 included instrumentalists (n = 26, mean age: 17.73 ± 2.83 y), while Group 2 and Group 3 consisted of vocalists (n = 30, mean age: 19.30 ± 2.47 y) and non-musicians (n = 30, mean age: 18.20 ± 3.02 y) respectively. The binaural processes namely integration (Dichotic syllable test, DST; and virtual acoustic space identification - VASI) and interaction (Interaural difference thresholds for time and level: ITD & ILD), were administered on all the participants. ResultsStatistical analyses showed the main effect of musicianship. Bonferroni pair-wise test revealed that the musicians (instrumentalists and vocalists) outperformed (p < 0.05) non-musicians in all the tests. The differential advantage of the musical background was seen on the binaural integration test with instrumentalists performing better in the VASI test compared to vocalists, and vice-versa for DST. No difference was observed in interaction tasks (ITD & ILD) between vocalists and instrumentalists (p > 0.05). ConclusionMusical background-induced differential advantages can be reasonably noted in the binaural skills of instrumentalists and vocalists (compared to non-musicians).

Binaural Processing and Auditory Working Memory in Individuals with Tinnitus Having Normal Hearing Sensitivity.

Tinnitus is a sound perceived in the ears or head without any external or internal sound source. It can be hypothesized that the auditory processing at the different levels of the auditory pathway and working memory may get affected due to the additional sound contributed by tinnitus. The objective of our study is to evaluate binaural processes and working memory capacity in individual with tinnitus having normal hearing sensitivity. The binaural interaction process was evaluated using the interaural time difference and interaural level difference. Similarly, the binaural integration process was assessed using the dichotic consonant-vowel test, and the working memory was assessed using the audio descending span test and Audio 2N-Back span test. Mann-Whitney U test was done to see the significant difference between the groups. The Mann-Whitney U test showed significantly poorer interaural level difference scores in the tinnitus group. Also, dichotic consonantvowel test scores and auditory working memory test scores were found to be significantly lower in individuals with tinnitus. The binaural processes, along with the working memory capacity, are found to be affected in an individual with tinnitus, which in turn may affect the speech perception ability of the individual.