Successful and unsuccessful users of bilateral amplification: Differences and similarities in binaural performance

Abstract

Abstract

Bilateral amplification seems to be the best solution for bilaterally hearing-impaired persons. Nevertheless, some individuals are unsuccessful with this strategy. The goals of the present study were to develop tests to improve the diagnostic test battery before rehabilitation of hearing-impaired persons with bilateral or unilateral amplification, and to evaluate the tests with normally-hearing subjects and with two groups of hearing-impaired persons. The latter two groups contained 11 successful and 11 unsuccessful users of bilateral amplification respectively. Hearing thresholds, speech recognition in noise, signal analysis ability, binaural abilities, and dichotic tests were used in the investigation. The subjects answered a questionnaire and hearing aid gain curves were measured. The results for the two groups were similar for peripheral hearing functions and binaural performance. The unilateral amplification group showed significantly worse results in speech-in-noise and dichotic tests. Spatial aspects within the questionnaire were correlated to amplification preference. We therefore suggest the inclusion of speech-in-noise, dichotic tests, and questions on spatial orientation into the diagnostic scheme before rehabilitation with hearing aids.

Sumario

La amplificación bilateral parece ser la mejor solución para las personas con daño auditivo bilateral. Sin embargo, algunos individuos no tienen éxito con esta estrategia. Las metas del presente estudio fueron desarrollar pruebas para mejorar la batería diagnósticas de exámenes antes de la rehabilitación de personas hipoacúsicas con amplificación unilateral o bilateral, y evaluar las pruebas en personas con audición normal, y con dos grupos de personas con daño auditivo. Los últimos dos grupos incluían 11 usuarios exitosos y 11 usuarios no exitosos de amplificación bilateral, respectivamente. Se utilizaron en esta investigación umbrales auditivos, reconocimiento de lenguaje en ruido, capacidad de análisis de la señal, capacidades binaurales y pruebas dicóticas. Los sujetos contestaron un cuestionario y se midieron las curvas de ganancia para auxiliares auditivos. Los resultados para los dos grupos fueron similares para las funciones auditivas periféricas y para el desempeño binaural. El grupo de amplificación unilateral mostró resultados significativamente peores en las pruebas dicóticas y de lenguaje en ruido. Los aspectos espaciales dentro del cuestionario se correlacionaron con las preferencias en la amplificación. Sugerimos, por tanto, la inclusión de pruebas dicóticas, de lenguaje en ruido y preguntas sobre orientación espacial en el esquema diagnóstico antes de la rehabilitación con auxiliares auditivos.

Key Words:

• Bilateral hearing aids
• Binaural hearing
• Speech recognition
• Signal analysis performance
• Dichotic listening
• Interhemispheric transfer

Acknowledgements

This work was supported mainly by grants from the Swedish Association of Hard of Hearing People, the Stinger Foundation (Foundation for audiological research), and Stiftelsen Tysta Skolan. The authors also wish to express their gratitude to Matthias Hällgren for generously providing us with the dichotic test material, Martin Dahlquist for his support in establishing contact with the subjects in the HI groups, and Anders Nästén for performing the hearing aid measurements. We also wish to thank Karolina Smeds for a discussion on ‘less than normal loudness’ and for letting us use her calculation routine for the NAL-R formula. We are thankful to Ulf Rosenhall and two anonymous reviewers for valuable comments on earlier versions of this manuscript.

The study was approved by the Regional Ethical Review Board in Stockholm, Dnr 2005/832-31/3.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.