Rejimon, Jwala

Stecker, G. Christopher

Carolina Digital Repository

Spectral Weighting Analysis of Sound Localization with Simulated EAS ListenersJwala Rejimon, B.S.1 , G. Christopher Stecker, Ph.D.2 School of Medicine, The University of North Carolina at Chapel Hill1, Spatial Hearing Lab, Boys Town National Research Hospital, Omaha, NE2INTRODUCTIONAIMS• To investigate the individual contributions of the different frequencybands in simulated EAS listening conditions• To determine the dependence of perceptual weighting on the degree ofspectral overlapMETHODSEXPERIMENT 1:EXPERIMENT 2:• To investigate if binaural interference reflects obligatory weighting of thespectral region of the interferer• To determine if listeners can volitionally shift weight off the distractor andonto the target (ignore the centered click trains and localize the noise)PARTICIPANTS:METHODSN Age Range Gender (M/F)Listeners 11 22—53 10 F, 1 MAll participants had self-reported normal hearing—no audiometric testing wasperformed due to the remote nature of the experiment.STIMULI:Figure 1: Stimuli consistedof 4 Gabor click trains and 3low-frequency bands ofnoise. In conditions A—D,various components of thestimuli were silenced toobserve how the perceptualweights would shift as thedegree of spectral overlapwas manipulated. Thestimulus duration was setto 100 milliseconds and thepresentation level was 60dB SPL per component.TASK AND APPARATUS:PROCEDURES AND ANALYSIS:• All testing and consenting was done remotely• Testing equipment was sanitized and delivered to participants’ residencesin a contactless manner• Participants completed 6 runs of conditions A through D, presented incounterbalanced order, followed by 8 consecutive runs of condition F• Multiple linear regression was used to relate the participants’ rank-transformed responses onto the actual ILD and ITD values of eachcomponent (See Folkerts and Stecker, 2019)Figure 2: ITD and ILD values applied to each component were calculated as the sum of ashared “base” ITD and ILD (shared across all components) and a unique “jitter” ITD andILD (assigned randomly and independently across components and trials). In Experiment2, however, the click trains remained centered while the noise bands were to be localized.RESULTSFigure 4: Spectral Weighting Functions are shown for conditions A through F.Findings suggest that ITD weights were consistently highest in the 400—1000Hzregions. In Experiment 2, where the click trains served as distractors and the taskwas to localize only the noise, the results were highly variable across subjects.CONCLUSIONSREFERENCESACKNOWLEDGMENTSBilsen and Raatgever. (1973). Spectral Dominance in Binaural Lateralization. Acustica. Volume 28, Heft 2. Folkerts and Stecker. (2019). SWF from Folkerts & Stecker (in Prep; ARO 2cvo019). Gifford, R. H., & Stecker, G. C. (2020). Binaural cue sensitivity in cochlear implant recipients with acoustic hearing preservation. Hearing research, 390, 107929. Gifford, R. H., Davis, T. J., Sunderhaus, L. W., Menapace, C., Buck, B., Crosson, J., O'Neill, L., Beiter, A., & Segel, P. (2017). Combined Electric and Acoustic Stimulation With Hearing Preservation: Effect of Cochlear Implant Low-Frequency Cutoff on Speech Understanding and Perceived Listening Difficulty. Ear and hearing, 38(5), 539–553. Van Ginkel, C., Gifford, R. H., & Stecker, G. C. (2019). Binaural interference with simulated electric acoustic stimulation. The Journal of the Acoustical Society of America, 145(4), 2445–2452. IMPLICATIONS:• Experiment 1 results exhibit a pattern of perceptual weight beinghighest between 400Hz and 1000Hz. This concurs with prior research inthe lab (Folkerts and Stecker, 2019) and is consistent with previouslyestablished “ITD dominance region” (Bilsen and Raatgever, 1973).• Experiment 2 results exhibit a slight pattern of volitional shifting ofperceptual weight from the click trains to the noise bands, but there ishigh variability between subjects.• Some subjects in Experiment 2 displayed improvement in their ability toshift perceptual weight—this indicated a possibility of learning.• Ability to reproduce booth testing using virtual reality (VR) headsetopens up possibilities for remote binaural cue testing in future research• Possibility of expanding VR testing into clinical settings• Members of the Spatial Hearing Lab, particularly Julie Stecker and Monica Folkerts fortheir help and contributions• Support for this study is provided by the National Institute of Health T35 DC008757 andR01 DC016643• COI Disclosure: GCS is a member of Auditory Space LLC., developers of A-SPACE software• Van Ginkel et al. (2019) investigated this by measuring ITD/ILDthresholds in low-frequency noise bands with high-frequency Gaborclick train (GCT) distractors.• They found that interference effects were positively correlated withthe degree of spectral overlap between the target and distractor.• In this study, we followed up on Van Ginkel’s experiment byinvestigating the specific contributions of the different frequencycomponents in simulated EAS binaural hearing conditions.Binaural interference refers to the reduction of binaural cue sensitivity ina target stimulus in the presence of a spectrally remote interferer. BinauralInterference is thought to especially impact hearing-impaired patients withelectric-acoustic stimulation devices (EAS) due to the possibility of conflictinginformation.Figure 3: Stand-alone virtual reality (VR) headset and circumaural headphones (see Figure5) were used in conjunction with a customized version of A-SPACE, a program developedby one of the authors (GCS) to control perceptual experiments in VR..1-.2 .2-.4 .4-.8 1 2 4 8 .1-.2 .2-.4 .4-.8 1 2 4 800.20.4Mean Wt (+/- 95% ci) Condition A (GCT only)ITD weights ILD weights.1-.2 .2-.4 .4-.8 1 2 4 8 .1-.2 .2-.4 .4-.8 1 2 4 800.20.4Mean Wt (+/- 95% ci) Condition B (400-800 Hz Gap).1-.2 .2-.4 .4-.8 1 2 4 8 .1-.2 .2-.4 .4-.8 1 2 4 8-0.200.20.4Mean Wt (+/- 95% ci) Condition C (1 kHz Gap).1-.2 .2-.4 .4-.8 1 2 4 8 .1-.2 .2-.4 .4-.8 1 2 4 800.20.4Mean Wt (+/- 95% ci) Condition D (Full Complex).1-.2 .2-.4 .4-.8 1 2 4 8 .1-.2 .2-.4 .4-.8 1 2 4 8Component Freq (kHz)00.51Mean Wt (+/- 95% ci) Condition F (Noise Target, GCT Distractor)component presentcomponent absentITD weights ILD weightsITD weights ILD weightsITD weights ILD weightsITD weights ILD weightsLIMITATIONS:• Unable to audiometrically verify that participants had normal hearing• Heterogeneity across subjects and high variability in Condition F• Testing over headphones produces an internalized percept whereas afree-field set-up produces an externalized percept of the soundFigure 5: A standalone VR headset (OculusQuest 2) along with calibrated circumauralheadphones (Sennheiser HD 280) were usedto deliver auditory and visual stimuli.EAS PATIENTSMay not agree with each other Possibility of Interference0.1 0.2 0.4 0.8 1  2  4  8  Freq (kHz)D/FCBA1 kHz 2 kHz 4 kHz 8 kHz2 kHz 4 kHz 8 kHz1 kHz 2 kHz 4 kHz 8 kHz1 kHz 2 kHz 4 kHz 8 kHz                      L;l; Trial 1           Trial 2 ITD value 

Spectral Weighting Analysis of Sound Localization with Simulated EAS Listeners

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Spectral Weighting Analysis of Sound Localization with Simulated EAS Listeners

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