Binaural Presentation Research Articles

Gender disparity in subcortical encoding of binaurally presented speech stimuli: An auditory evoked potentials study

To investigate the influence of gender on subcortical representation of speech acoustic parameters where simultaneously presented to both ears. Two-channel speech-evoked auditory brainstem responses were obtained in 25 female and 23 male normal hearing young adults by using binaural presentation of the 40 ms synthetic consonant-vowel/da/, and the encoding of the fast and slow elements of speech stimuli at subcortical level were compared in the temporal and spectral domains between the sexes using independent sample, two tailed t-test. Highly detectable responses were established in both groups. Analysis in the time domain revealed earlier and larger Fast-onset-responses in females but there was no gender related difference in sustained segment and offset of the response. Interpeak intervals between Frequency Following Response peaks were also invariant to sex. Based on shorter onset responses in females, composite onset measures were also sex dependent. Analysis in the spectral domain showed more robust and better representation of fundamental frequency as well as the first formant and high frequency components of first formant in females than in males. Anatomical, biological and biochemical distinctions between females and males could alter the neural encoding of the acoustic cues of speech stimuli at subcortical level. Females have an advantage in binaural processing of the slow and fast elements of speech. This could be a physiological evidence for better identification of speaker and emotional tone of voice, as well as better perceiving the phonetic information of speech in women.

Stuttering inhibition via altered auditory feedback during scripted telephone conversations

Overt stuttering is inhibited by approximately 80% when people who stutter read aloud as they hear an altered form of their speech feedback to them. However, levels of stuttering inhibition vary from 60% to 100% depending on speaking situation and signal presentation. For example, binaural presentations of delayed auditory feedback (DAF) and frequency-altered feedback (FAF) have been shown to reduce stuttering by approximately 57% during scripted telephone conversations. To examine stuttering frequency under monaural auditory feedback with one combination of DAF with FAF (COMBO-2) and two combinations of DAF with FAF (COMBO-4) during scripted telephone conversations. Nine adult participants who stutter called 15 local businesses during scripted telephone conversations; each condition consisted of five randomized telephone calls. Conditions consisted of (1) baseline (i.e. non-altered feedback), (2) COMBO-2 (i.e. 50-ms delay with a half octave spectral shift up), and (3) COMBO-4 (i.e. 200-ms delay and a half octave spectral shift down in addition to the COMBO-2). Participants wore a supra-aural headset with a dynamic condenser microphone while holding a receiver to their contralateral ear when making telephone calls. Stuttering was significantly reduced during both altered auditory feedback (AAF) conditions by approximately 65%. Furthermore, a greater reduction in stuttering was revealed during the COMBO with four effects (74%) as compared with the COMBO with two effects (63%). Results from the current study support prior research reporting decreased stuttering under AAF during scripted telephone conversations. Findings that stuttering was significantly reduced to a greater extent under the COMBO with four effects condition suggest that second signals reduce stuttering along a continuum. Additionally, findings support prior research results of decreased stuttering frequency under AAF during hierarchically difficult speaking situations. Clinical application of these findings may be that people who stutter can use specific software or smartphone applications that produce second speech signals to inhibit stuttering frequency effectively during telephone conversations.

Magnetoencephalographic Study on Forward Suppression by Ipsilateral, Contralateral, and Binaural Maskers

When two tones are presented in a short time interval, the response to the second tone is suppressed. This phenomenon is referred to as forward suppression. To address the effect of the masker laterality on forward suppression, magnetoencephalographic responses were investigated for eight subjects with normal hearing when the preceding maskers were presented ipsilaterally, contralaterally, and binaurally. We employed three masker intensity conditions: the ipsilateral-strong, left-right-balanced, and contralateral-strong conditions. Regarding the responses to the maskers without signal, the N1m amplitude evoked by the left and binaural maskers was significantly larger than that evoked by the right masker for the left-strong and left-right-balanced conditions. No significant difference was observed for the right-strong condition. Regarding the subsequent N1m amplitudes, they were attenuated by the presence of the left, binaural, and right maskers for all conditions. For the left- and right-strong conditions, the subsequent N1m amplitude in the presence of the left masker was smaller than those of the binaural and right maskers. No difference was observed between the binaural and right masker presentation. For left-right-balanced condition, the subsequent N1m amplitude decreased in the presence of the right, binaural, and left maskers in that order. If the preceding activity reflected the ability to suppress the subsequent activity, the forward suppression by the left masker would be superior to that by the right masker for the left-strong and left-right-balanced conditions. Furthermore, the forward suppression by the binaural masker would be expected to be superior to that by the left masker owing to additional afferent activity from the right ear. Thus, the current results suggest that the forward suppression by ipsilateral maskers is superior to that by contralateral maskers although both maskers evoked the N1m amplitudes to the same degree. Additional masker at the contralateral ear can attenuate the forward suppression by the ipsilateral masker.

Electrophysiological Measures of Auditory Processing in Patients with Multiple Sclerosis

Previous studies demonstrated that patients with multiple sclerosis (MS) experience more hearing loss than age-matched control subjects. Patients with MS also exhibit deficits processing auditory stimuli, including speech in a background of noise. These findings suggest that auditory deficits in the MS population can result from damage to central neural pathways in addition to peripheral hearing structures. To assess auditory processing functions in patients with MS, this study used auditory event-related potentials (AERPs)—specifically, the auditory brain stem response (ABR) and long-latency AERPs including the P300. AERPs recorded from 20 patients with MS were compared to AERPs from 20 healthy control subjects. When ABR stimuli (clicks) were presented monaurally, there were no significant differences between groups in component latencies or amplitudes for waves I through V. However, binaural presentation of the same stimuli elicited wave V ABR components significantly greater in amplitude for the control group compared with the MS group. Long-latency AERP results showed no significant differences between groups for N100 latency and amplitude or for P300 latency. P300 component amplitude was significantly greater for control subjects compared with patients with MS. It is probable that neural degeneration and impaired neural transmission within the MS group contributed to these AERP results. AERPs are useful tools that can be used to assess peripheral and central auditory functions as well as cognitive processing abilities in patients with MS. AERPs could be used to evaluate neural integrity, disease progression, and treatment efficacy in this population.

Performance of binaural technology for auditory selective attention

A room-acoustic situation with many sources is one of the best examples for auditory selective attention – relevant information should be selectively observed and irrelevant information should be ignored. In a joint research project between Acoustics and Psychology at RWTH Aachen University the intentional switching of auditory selective attention is examined using dichotic and binaural presentation of the stimuli. The goal is to provide artificially generated acoustic scenes (e.g. typical classroom situation, open plan offices etc.), as in psychoacoustic experiments on auditory selective attention no differences between a real situation and an artificially generated situation occur. Therefore at first we investigate various binaural reproduction and equalization methods using experiments in auditory selective attention. Headphones must always be adequately equalized if they are to deliver high perceptual plausibility. However, the transfer function between headphones and ear drums varies between different persons. Because of this, individual equalizations with different microphone positions in the ear canal are measured. In listening tests the overall quality of the equalization methods is to be rated regarding localization and realism, envelopment as well as immersion. First results concerning the psychoacoustic experiments, the scene generation as well as headphone equalization will be presented.

Listening to White Noise Counteracts Visual and Haptic Pseudoneglect

Neurologically intact individuals usually show a leftward bias in line bisection, a tendency known as "pseudoneglect", likely reflecting a right-hemisphere dominance in controlling the allocation of spatial attention. Studies in brain-damaged patients with left visuospatial neglect have reported that auditory stimulation may reduce the deficit, both in a spatially dependent and in a spatially independent way. Here we show for the first time that the concurrent binaural presentation of auditory white noise affects healthy individuals' performance in both visual and haptic bisection, reducing their leftward error. We suggest that this effect depends on the noise boosting alertness and restoring the hemispheric activation balance. Our data clearly show that task-irrelevant auditory noise crossmodally affects the allocation of spatial resources in both the haptic and the visual space; future research may clarify whether these effects are specific for the type of auditory stimulation.

Binaural dichotic presentation to reduce the effects of spectral masking in moderate bilateral sensorineural hearing loss

Objective: The objective of the study was to evaluate the effectiveness of binaural dichotic presentation using comb filters with complementary magnitude responses, based on fixed bandwidth and auditory critical bandwidth, in improving speech perception by persons with moderate bilateral sensorineural hearing loss, and to assess its effect on localization of the sound source. Design and Study sample: Listening tests involving consonant recognition and source direction identification were conducted on six normal-hearing subjects under simulated hearing loss and on eleven subjects with moderate bilateral sensorineural loss in quiet. Results: The tests on normal-hearing subjects showed higher recognition scores and smaller response times for the comb filters based on the auditory critical bandwidth. The tests using these comb filters on the hearing-impaired subjects resulted in an increase of 14%–31% (mean: 22%) in recognition scores and a significant decrease in response times, with no significant effect on the identification of the direction of broadband sound sources. Conclusions: The results show that dichotic presentation may be useful for speech processing in binaural hearing aids.

Affective priming with auditory speech stimuli

Four experiments explored the applicability of auditory stimulus presentation in affective priming tasks. In Experiment 1, it was found that standard affective priming effects occur when prime and target words are presented simultaneously via headphones similar to a dichotic listening procedure. In Experiment 2, stimulus onset asynchrony (SOA) was varied in the same procedure. Significant priming effects occurred only when prime and target stimuli were presented simultaneously or partly overlapping (SOA = 250 ms), but not if they were presented clearly separable (SOA = 500 ms). In Experiment 3, an auditory masking procedure was implemented with binaural prime and target presentation to demonstrate that auditory priming effects also occur under conditions of limited prime awareness. In Experiment 4, an unmasked auditory priming procedure with binaural prime and target presentations generated comparable affective priming effects in a social attitude domain (i.e., intergroup attitudes). Results of all four experiments show that affective priming effects can be found with auditory presented stimuli, thus enlarging the tool box of affective priming research.

A Novel Binaural Pitch Elicited by Phase-Modulated Noise: MEG and Psychophysical Observations

Binaural pitches are auditory percepts that emerge from combined inputs to the ears but that cannot be heard if the stimulus is presented to either ear alone. Here, we describe a binaural pitch that is not easily accommodated within current models of binaural processing. Convergent magnetoencephalography (MEG) and psychophysical measurements were used to characterize the pitch, heard when band-limited noise had a rapidly changing interaural phase difference. Several interesting features emerged: First, the pitch was perceptually lateralized, in agreement with the lateralization of the evoked changes in MEG spectral power, and its salience depended on dichotic binaural presentation. Second, the frequency of the pure tone that matched the binaural pitch lay within a lower spectral sideband of the phase-modulated noise and followed the frequency of that sideband when the modulation frequency or center frequency and bandwidth of the noise changed. Thus, the binaural pitch depended on the processing of binaural information in that lower sideband.

How can a video game cause panic attacks? I. Effects of an auditory stressor on the human brainstem.

The auditory brainstem response (ABR) was recorded during simultaneous binaural presentation of two types of sounds: (1) condensation clicks presented through in-the-ear earphones at 43.1/s, 60 dB nHL; and (2) recordings of breathing sounds, presented through supra-aural headphones, at levels adjusted by participants to be equivalent to the clicks. In alternate blocks, the breathing sounds were either: (1) a recording of quiet breathing (blocks 1, 3, and 5) or (2) a recording of erratic (stressed) breathing (blocks 2 and 4). The erratic breathing was modeled on a video game soundtrack in which the character was represented as running, wounded, and frightened. Four 2048-sweep ABR waveforms were collected in each of the five blocks, and the mean amplitude of ABR peak V was calculated over each set of four waveforms. Results indicate a significant decrease in the amplitude of ABR peak V during erratic breathing versus quiet breathing. Implications include (1) possible new evidence of the effect of selective attention on the ABR, (2) the potential for using auditory stressors to study the central physiology of emotional responses in humans, and (3) clues to physiological correlates of the effects of certain video games known to evoke panic attacks in susceptible players.

Effects of Contralateral Noise on 40-Hz and 80-Hz Auditory Steady-State Responses

The amplitude of 40-Hz auditory steady-state response (ASSR) in response to repeated click or tone pips at levels of 45 to 60 dB SL is reduced by up to 50% by the central masking mechanism if white noise at levels of 40 to 60 dB SL is applied contralaterally. However, the effect of contralateral noise on the elevation of the threshold of ASSR is unknown. The present study investigated the effects of contralateral noise on the threshold measurements of ASSR for 40- and 80-Hz amplitude modulated tones that are widely used in clinical examinations. The effects of contralateral noise on the 40- and 80-Hz ASSRs for amplitude modulated tones at 500 Hz and 2000 Hz were examined in 11 healthy volunteers (10 men and 1 woman, mean age 26.1 years). Contralateral noise consisted of white noise low-pass filtered at 700 and 4000 Hz in the measurements of ASSR at a carrier frequency of 500 and 2000 Hz, respectively. Contralateral noise at a level of 40 dB SL caused no significant psychophysical threshold elevation, caused significant threshold elevation of the 40-Hz ASSR (average 10 to 15 dB), and caused no significant threshold elevation of the 80-Hz ASSR. The different effects on the 40- and 80-Hz ASSRs were probably related to the differences in sources because the 40-Hz ASSR contains more components from the upper auditory pathway that are affected by contralateral masking, whereas the 80-Hz ASSR contains more components from the brain stem. The present results suggest that threshold elevation of the 40-Hz ASSR may occur during clinical measurements using binaural presentation of sounds and cause a possible discrepancy between psychophysical threshold and 40-Hz ASSR measurements.

Auditory pathways fail to re-establish normal cortical activation patterns in response to binaural stimulation following a unilateral lesion of the inferior colliculus

The aim of this study was to investigate cortical activation in response to binaural stimulus presentations in an individual (FX) with a circumscribed traumatic hemorrhagic lesion of the right inferior colliculus. FX and control subjects were exposed to complex sounds while undergoing a functional magnetic resonance imaging assessment. Whereas normally-hearing individuals show well-balanced bilateral activation patterns in response to binaural auditory stimulation, the same stimuli produced stronger activation in the left hemisphere in FX. Combined with previous data, these findings reinforce the notion that the inferior colliculus is an essential auditory relay and that its loss cannot be significantly compensated.

Binaural Dichotic Presentation of Speech Signal for Improving its Perception to Sensorineural Hearing-Impaired using Auditory Filters

Sensorineural hearing loss relates to spread of spectral masking resulting in reduction in frequency resolving capacity. Such hearing-impaired persons find difficulties while identifying consonantal ‘place’ feature cued by spectral differences. In binaural dichotic presentation scheme splitting of speech signal in real-time into two signals with complementary short-time spectra using filters with magnitude response based on two auditory filter banks with linear phase was implemented and evaluated. Filter banks corresponding to eighteen critical bands over 5 kHz frequency range were used. Listening tests were performed on subjects with ‘mild73x2019; to ‘very severe’ bilateral sensorineural hearing loss. The usefulness of the scheme for better reception of spectral characteristics was evident as the results indicated improvement in speech quality, response time, recognition scores and transmission of ‘place’ feature particularly.

Activation of human auditory cortex during speech perception: Effects of monaural, binaural, and dichotic presentation

We used a rapid event-related functional magnetic resonance imaging (fMRI) paradigm to compare cortical activation to speech tokens presented monaurally to each ear, binaurally, and dichotically. Two forms of dichotic conditions were examined: one presented consonant-vowel (CV) syllables simultaneously to each ear while the other paired a CV syllable with a non-speech stimulus (band-limited noise). Right-handed adults were asked to differentially respond to serially presented target and distractor CV syllables. Activations were localized with reference to anatomic segmentation algorithms that allowed us to distinguish between activity in primary (PAC) and non-primary auditory cortex (NPAC). Monaural CV syllables presented to the right ear (CVR) produced highly asymmetric activations in left PAC and NPAC. A similar but reduced left hemisphere (LH) bias was evident in binaural presentation, when monaural syllables were paired with contra-aural noise, and in dichotic CV–CV presentations. However, LH activation was two times larger to CVR than any other condition, while RH activation to CVR was insubstantial. By contrast, a small rightward asymmetry in PAC activation was observed from monaural left ear (CVL) presentation. In all conditions except CVL, magnitude of response favored left PAC and NPAC. CV processing across different listening conditions disclosed complex interactions in activation. Our results confirm the superiority of left NPAC in speech processing and suggest comparable left lateralization in PAC. The findings suggest that monaural CV presentation may be more useful than previously anticipated. The paradigm developed here may hold some promise in investigations where abnormal hemispheric balance of speech processing is suspected.

Human efferent adaptation of DPOAEs in the L1, L2 space

The adaptive properties of distortion product otoacoustic emissions (DPOAEs) at 2 f 1 − f 2 were investigated in 12 ears of normally hearing adults aged 18–30 years using long-lasting 1-s primary-tone on-times. In this manner, DPOAE adaptation at a single f 2 of 1.55 kHz ( f 2/ f 1 = 1.21) was evaluated as a function of the levels of the primary tones in a matrix of L 1, L 2 settings, which varied from 45 to 80 dB SPL, in 5-dB steps. DPOAEs were elicited under both monaural and binaural stimulus-presentation conditions. Adaptation was defined as the difference in DPOAE levels between the initial 92-ms baseline measure using a standard protocol and one obtained during the final 92 ms of the prolonged 1-s primary-tones. These differences were averaged across subjects to create contour plots of mean adaptation in the L 1, L 2 space. The 2 f 1 − f 2 DPOAE revealed consistent regions of suppression (⩽−0.5 dB difference) or enhancement (⩾+0.5 dB difference) with respect to baseline measures within the L 1, L 2 matrix for both acoustic-stimulation conditions. Specifically, 2 f 1 − f 2 DPOAE suppressions of 1–2 dB occurred for both monaural and binaural presentations, typically at level combinations in which L 1 > L 2. In contrast, larger 2 f 1 − f 2 DPOAE enhancements of 3–4 dB occurred for only the binaural condition, at primary-tone level combinations where L 1 < L 2. Although adaptation activity was also evaluated for the DPOAEs at f 2 − f 1, 2 f 2 − f 1, and 3 f 1 − 2 f 2, these emissions were either immeasurable (e.g., f 2 − f 1) or only present in a subset of subjects over a narrow range of primary-tone frequencies and levels that did not support a systematic analysis. In summary, the 2 f 1 − f 2 results suggest that a potentially important area for adaptation measures exists in the L 1, L 2 space, when L 1 is lower than L 2. This combination of primary-tone levels can lead to large DPOAE adaptation effects that may be related to a notch in the DPOAE response/growth or input/output (I/O) function.

Functional asymmetry in human primary auditory cortex: Identified from longitudinal fMRI study

The leftward hemispheric dominance in language processing may be associated with fundamental functional asymmetry in the primary auditory cortex (PAC). Based on repeated functional MRI (fMRI) measurements, we investigated the presence of functional asymmetry in the human PAC using binaural presentation of linguistic sounds (two-syllable nouns) and simple tonal stimulation. Eight right-handed volunteers underwent nine fMRI sessions, approximately eight weeks apart, spanning the duration of more than a year. The PAC from each hemisphere was manually segmented and the volume of activation, detected within the segmented region-of-interest, was measured across the subjects and sessions to generate functional laterality indices. Although variations existed in activation volume between sessions and subjects, we found predominant and consistent leftward functional asymmetry in PAC during both linguistic and non-linguistic sound stimulations.

Intelligibility and preferred rate of Chinese speaking

This research was conducted to investigate the relationship between the rate of natural speech and intelligibility, and to examine the effects that some subject and task factors may have on Chinese speech perception. Other than the objective measure of speech intelligibility, subjective preferences of listeners towards speech rate and presentation mode were also investigated. Sixty subjects performed a set of intelligibility tests and subjective preference evaluations. The results indicated that at the rate of 4.3 characters per second (231 ms per character) previously established for professional newscasters, subjects perceived information with correctness of up to 99% and a maximum preference level was observed. Speech rates and presentation modes that were preferred by the subjects were also more easily intelligible. There was a binaural advantage over the monaural mode of presentation in speech intelligibility, and subjects generally preferred the binaural presentation to the monaural presentation. An accurate prediction of speech intelligibility was possible based on age of listener, presentation mode, and speech rate. The older subjects perceived speech less accurately and preferred slower speech than the younger subjects. The study demonstrated the importance of considering subject and task factors for compilation of standard speaking time for practical applications. Relevance to industry The results of this study are useful in generating a category of basic Chinese speaking times for standardizing speech performance and prediction of speech intelligibility and preference ratings of listeners under different listening conditions. In the reverse, the speaking rate for a certain intelligibility level can be estimated for practical use if detailed listening conditions are known.

Bilateral cochlear implantation and directional multi-microphone systems

Better speech understanding in noise is a common goal of bilateral cochlear implantation and directional multi-microphone systems. In this study, the performance of five signal processing/presentation strategies is compared: (1) monaural presentation using a single omnidirectional microphone, (2) monaural presentation using a simple two-microphone beamformer in a behind-the-ear (BTE) housing, (3) monaural presentation using a complex four-microphone adaptive beamformer, (4) binaural presentation using two omnidirectional microphones and (5) binaural presentation using two simple two-microphone beamformers in separate behind-the-ear units. Speech reception thresholds (SRT) in noise were measured in four adults implanted bilaterally with MED-EL cochlear implant systems. Speech was presented from the front and speech spectrum noise from an azimuth of 90°. For all conditions involving microphones at only one ear, the noise source was placed at the contralateral side. Average speech reception threshold (SRT) improvements over the single omnidirectional microphone (condition 1) were 3.0 dB for the simple two-microphone BTE beamformer, 1.8 dB for bilateral cochlear implants and 3.6 dB for the combination of both. The largest mean improvement (13.0 dB) was achieved by the complex four-microphone beamformer. Bilateral cochlear implants and multi-microphone beamforming seem to complement each other but are outperformed by complex signal processing strategies in this laboratory setting.

Phonemic contrasts in a mutiple talker task with hearing impaired listeners

Word identification ability of mild to moderately hearing impaired listeners was measured in both spatial and nonspatial multiple talker tasks. A digital recording of the modified rhyme test was made for three male talkers. The beginning of the test word in each phrase was synchronized using Cool Edit and equalized to the same average rms power. The phrases were processed for binaural presentation using nonindividualized HRTFs with Tucker Davis Technology System 3 equipment and presented over Sennheisser 600 headphones. The phrases were presented in random order at a self-paced manner. Five mild and five moderately hearing impaired subjects, ranging in age from 24 to 54 years, participated in this study. Results were analyzed by six attributes: place, voicing, nasality, frication, duration, and stops. Phoneme identification performance was ranked based on most salient (most information transferred) to least salient (least information transferred). Spatial separation had no effect on the relative importance of the speech attributes. Duration was the most salient cue for hearing impaired listeners, followed by voicing and frication. Stops and nasality were weak cues and place was by far the least important cue.

The Role of Phase Changes in Sound Signals in Localization of Sound Sources

The auditory system in humans and animals makes virtually no discrimination of phase changes in the structure of monaurally presented sound signals. However, electrophysiological studies have demonstrated marked changes in the responses of the central parts of the auditory system when the phase structure of the signal changes during presentation of the same type of stimulation. We have suggested that this inconsistency is due to the preparative role of phase effects during monaural stimulation for subsequent operations in the auditory system involved in determining the location of a sound source in space. This report presents experimental data on defined changes (increases in amplitude) in the electrical responses of the midbrain center of the auditory system (inferior colliculus) in antiphase binaural presentation of series of sound impulses (comparison with synphase presentation). These changes may be part of the mechanism underlying the interference resistance of the auditory system during determination of the location of a sound source (binaural release from masking). Neuronal cortical activity is sensitive and selective to dynamic interaural changes in the phase spectrum of the signal, which may provide the basis of the mechanism for locating a moving sound source. Auditory evoked potentials in humans demonstrate memorizing of the direction of movement of a sound image, as shown by the changes in parameters on presentation of stimuli of different locations (deviant stimuli) differing from the standard parameters of mismatch negativity.