Pure-tone audiometric threshold assessment with in-ear monitoring of noise levels

Abstract

Objective: Our objective was to obtain reliable threshold measurements without a sound booth by using a passive noise-attenuating hearing protector combined with in-ear 1/3-octave band noise measurements to verify the ear canal was suitably quiet. Design: We deployed laptop-based hearing testing systems to Tanzania as part of a study of HIV infection and hearing. An in-ear probe containing a microphone was used under the hearing protector for both the in-ear noise measurements and threshold audiometry. The 1/3-octave band noise spectrum from the microphone was displayed on the operator's screen with acceptable levels in grey and unacceptable levels in red. Operators attempted to make all bars grey, but focused on achieving grey bars at 2000 Hz and above. Study sample: 624 adults and 197 children provided 3381 in-ear octave band measurements. Repeated measurements from 144 individuals who returned for testing on three separate occasions were also analysed. Results: In-ear noise levels exceeded the maximum permissible ambient noise levels (MPANL) for ears not covered, but not the dB SPL levels corresponding to 0 dB HL between 2000–4000 Hz. In-ear noise measurements were repeatable over time. Conclusions: Reliable audiometry can be performed using a passive noise-attenuating hearing protector and in-ear noise measurements.

Key Words::

• Audiometry
• octave band measurements

Acknowledgements

Some of these data were presented at the 3rd Coalition for Global Hearing Health Conference in Pretoria, South Africa. We thank the team at the DarDar clinic in Dar es Salaam, Tanzania who collected these data (Esther Kayichile, Kissa Albert, Safina Sheshe, Claudia Gasana, Mariane Mpessa, and Joyce Joseph). We also appreciate the support from audiologists Machemba Lawrence and Alfred Mathayo. We thank the team at Creare Inc., that assembled and tested the hearing testing systems, particularly Jed Wilbur and Nathan Brown. We appreciate the support of Erika Kafwimi and Sabrina Yegela who helped with building the video questionnaire and translating the questions.

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

This work is supported by grant R01DC009972 from the National Institute on Deafness and Other Communication Disorders (NIDCD).