Interaural time (ITD) and level differences (ILD) are susceptible to distortion by multipath acoustics due to reverberation, echoes, and potentially with open-fit, behind-the-ear (BTE) hearing aids, which pose an additional delay between acoustic and processed sound (~2-5ms). Here, ten young, normal hearing listeners localized broadband and narrowband (500, 4000, 500+4000 Hz) noise. Listeners were fit with linear amplification and evaluated in three aided conditions: unaided, open-fit, and occluded BTE coupling. Sounds were presented from 64 loudspeakers covering 360º azimuth in an anechoic chamber. Twenty-three target locations were evaluated, spanning ±61º. Sounds were presented in three virtual acoustic environments: anechoic, single virtual wall, and simulated 10m X 10m room. The virtual wall was 80% reflective (α=0.2) and oriented parallel to the listenerâs forward gaze, at a distance of 5m to the right. The room condition simulated four virtual walls (α=0.5), 5m to the left and right, 6.67m in front, and 3.33m behind the listening position.
Performance was assessed across conditions by measuring localization gain (slope), localization variance, localization error, and front-back confusion rate. Results showed greater variability in the simulated room than anechoic conditions, particularly for aided conditions (occluded > open > unaided). Aided listening compressed localization gain at 4000 Hz and expanded gain at 500 Hz. Errors were generally reduced when 500 and 4000 Hz were played simultaneously.
Additionally, in-ear acoustic recordings of broadband noise were made in all aided and room conditions. Binaural cross-correlation and intensity-difference calculation were used to estimate frequency-specific ITD and ILD, respectively, from the recordings. Consistent with previous research, ITD became erratic and ILD diminished in simulated rooms compared to anechoic. Effects of hearing aid venting were less noticeable. Finally, results were quantified in the form of binaural-cue weighting (ITD/ILD âtrading ratioâ) on the basis of measured interaural cue values extracted from in-ear recordings obtained for each listener and condition.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-07212016-175018 |
| Date | 29 July 2016 |
| Creators | Diedesch, Anna Colleen |
| Contributors | G. Christopher Stecker, Todd A. Ricketts, D. Wesley Grantham, Daniel H. Ashmead, Frederick J. Gallun |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-07212016-175018/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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