The Acceptable Noise Level Benefit From Directionality for Listeners With Severe Hearing Loss

Clinical and Experimental Otorhinolaryngology Vol. 11, No. 3: 166-173, September 2018 https://doi.org/10.21053/ceo.2017.01375 pISSN 1976-8710 eISSN 2005-0720 Original Article The Acceptable Noise Level Benefit From Directionality for Listeners With Severe Hearing Loss Mina Aghsoleimani1·Hamid Jalilvand1·Mohammad Ebrahim Mahdavi1·Ahmad Reza Nazeri1·Mohammad Kamali2 Department of Audiology, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran; 1 Department of Basic Sciences, School of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran 2 Objectives. Directional microphone technology can enhance the speech intelligibility and listening comfort of listeners with hearing impairment. The main aim of this study is to investigate and compare the benefit derived by listeners with severe hearing loss from directional microphone technology with that derived by listeners with moderate hearing loss. Methods. The acceptable noise levels (ANLs) of two groups of listeners with moderate or severe hearing impairment (17 subjects in each group) were measured under unaided, omnidirectional-baseline-aided, and directional-aided conditions. Results. Although the absolute ANL of the listeners in the severe hearing loss group was significantly higher than that of the listeners in the moderate hearing loss group, their derived benefit was equivalent to that derived by the listeners in the moderate hearing loss group. ANL and hearing loss degree were significantly related. Specifically, the ANL increased with the severity of hearing loss. Conclusion. Directional microphone technology can provide the benefits of listening comfort to listeners with severe hearing loss. Keywords. Directional Hearing Aid; Hearing Aids; Acceptable Noise Level; Hearing Loss INTRODUCTION signal-to-noise ratio. By clarifying speech and lessening noise, this technology improves the listener’s ability to understand speech in noisy environments. The ability of directional hearing aids to improve speech perception under noisy conditions has been demonstrated by different studies, which utilized different variables, tools, and methodologies [1]. These studies, however, investigated speech perception in noise among participants with normal hearing [2], and mild to moderate hearing loss [1]. By contrast, speech performance in participants with severe hearing loss has not been widely investigated. Acceptable noise level (ANL) is a subjective measurement used to evaluate a subject’s performance in noise. The ANL was introduced by Nabelek et al. [3] as a test for evaluating a subject’s willingness to tolerate noise while listening to a running speech. It is quantified as the difference between the most comfortable level (MCL) of a running speech and the background noise level (BNL) of a competing babble noise tolerated by the subject (ANL=MCL–BNL). Listeners with a lower value of ANL can tolerate a higher level of noise than listeners with a The human auditory system enables the detection and discrimination of sounds and provides speech intelligibility in noise, a necessary ability lacking in a listener with sensorineural hearing loss. Thus, the ability to discern speech from noise is the main demand of many listeners with sensorineural hearing loss. Directional microphone technology is the main digital signal processing (DSP) technology employed in modern digital hearing aids to improve speech intelligibility. Directional microphones utilize multiple microphones or ports (at least two microphones or ports) and spatially separate speech from noise to improve ••Received October 3, 2017 Revised January 8, 2018 Accepted January 11, 2018 ••Corresponding author: Hamid Jalilvand Department of Audiology, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Damavand St., Tehran, Iran Tel: +98-21-7756-1721, Fax: +98-21-7759-1807 E-mail: Copyright © 2018 by Korean Society of Otorhinolaryngology-Head and Neck Surgery. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 166 Aghsoleimani M et al. The Acceptable Noise Level Benefit higher value of ANL. A high ANL indicates that the listener cannot tolerate a high level of noise. If a special DSP algorithm of the user’s hearing aid (for example, directional microphone) decreases noise, the user’s ANL decreases relative to a baseline condition under which the algorithm is not used. The ANL benefit, which is obtained by subtracting the ANL obtained under a specific condition from the ANL obtained under the baseline condition, can be used to show the effectiveness of a special technology for reducing noise. In addition, it is indicative of a subject’s listening comfort in noise. Thus, ANL can be used to evaluate the benefit provided by different hearing aid technologies. However, despite numerous studies on ANL and its application in various research designs, the belief that hearing loss and ANL result are unrelated continues to persist. In fact, all related studies on ANL have investigated subjects with normal hearing or mild to moderately severe sloping hearing loss. Studies on the ANL of subjects with severe hearing loss have not compared the ANL of the subjects under unaided and aided conditions [4] (for a thorough review, refer to [5]). A major original work from Nabelek et al. [6] investigated listeners with moderate sloping hearing loss. No study has compared the ANL results obtained under unaided or aided conditions of subjects with severe and less hearing loss. For example, a study on the ANL of participants with severe hearing loss did not present the details of hearing thresholds and did not compare the ANL results of the participants under unaided and aided conditions [7]. In addition, the real ear measurement (REM) was not used to verify amplification; thus, the conclusion and generality of the results of the study are unreliable. An Australian study [8], which included normal and hearing-impaired participants with different degrees of hearing losses, did not compare the ANL results obtained under unaided and aided conditions. Thus, the studies that utilized ANL to evaluate the effect of directional microphone technology have involved subjects with less than severe hearing loss. On the other hand, there are some factors that can influence ANL, such as audiogram configuration [9], speech intelligibility [10], binaural versus monaural directional amplification [11], duration of hearing aid usage [11], personality type [12], and H I G H L I G H T S Listeners with severe hearing loss still derived benefits from directional hearing aids that are equivalent to that derived by listeners with moderate hearing loss. The acceptable noise levels (ANLs) of the seve (...truncated)