J Am Acad Audiol 2020; 31(01): 017-029
DOI: 10.3766/jaaa.18048
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Interactions Between Digital Noise Reduction and Reverberation: Acoustic and Behavioral Effects

Paul Reinhart
*   Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL
Pavel Zahorik
†   Department of Psychological and Brain Sciences, University of Louisville, Louisville, KY
Pamela Souza
*   Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL
‡   Knowles Hearing Center, Evanston, IL
› Author Affiliations
Further Information

Publication History

19 February 2019

Publication Date:
25 May 2020 (online)



Digital noise reduction (DNR) processing is used in hearing aids to enhance perception in noise by classifying and suppressing the noise acoustics. However, the efficacy of DNR processing is not known under reverberant conditions where the speech-in-noise acoustics are further degraded by reverberation.


The purpose of this study was to investigate acoustic and perceptual effects of DNR processing across a range of reverberant conditions for individuals with hearing impairment.

Research Design:

This study used an experimental design to investigate the effects of varying reverberation on speech-in-noise processed with DNR.

Study Sample:

Twenty-six listeners with mild-to-moderate sensorineural hearing impairment participated in the study.

Data Collection and Analysis:

Speech stimuli were combined with unmodulated broadband noise at several signal-to-noise ratios (SNRs). A range of reverberant conditions with realistic parameters were simulated, as well as an anechoic control condition without reverberation. Reverberant speech-in-noise signals were processed using a spectral subtraction DNR simulation. Signals were acoustically analyzed using a phase inversion technique to quantify improvement in SNR as a result of DNR processing. Sentence intelligibility and subjective ratings of listening effort, speech naturalness, and background noise comfort were examined with and without DNR processing across the conditions.


Improvement in SNR was greatest in the anechoic control condition and decreased as the ratio of direct to reverberant energy decreased. There was no significant effect of DNR processing on speech intelligibility in the anechoic control condition, but there was a significant decrease in speech intelligibility with DNR processing in all of the reverberant conditions. Subjectively, listeners reported greater listening effort and lower speech naturalness with DNR processing in some of the reverberant conditions. Listeners reported higher background noise comfort with DNR processing only in the anechoic control condition.


Results suggest that reverberation affects DNR processing using a spectral subtraction algorithm in such a way that decreases the ability of DNR to reduce noise without distorting the speech acoustics. Overall, DNR processing may be most beneficial in environments with little reverberation and that the use of DNR processing in highly reverberant environments may actually produce adverse perceptual effects. Further research is warranted using commercial hearing aids in realistic reverberant environments.

This research was funded by the National Institutes of Health Grants F31 DC015373 to Paul Reinhart, R01 DC008168 to Pavel Zahorik and R01 DC006014 to Pamela Souza.

Portions of this work were presented at the 173rd Meeting of the Acoustical Society of America, Boston, MA, June 2017, and the 30th Annual Conference of the American Academy of Audiology, Nashville, TN, April 2018.


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