Using Auditory Steady-State Responses for Measuring Hearing Protector Attenuation.
BACKGROUND
Present methods of measuring the attenuation of hearing protection devices (HPDs) have limitations. Objective measurements such as field microphone in real-ear do not assess bone-conducted sound. Psychophysical measurements such as real-ear attenuation at threshold (REAT) are biased due to the low frequency masking effects from test subjects' physiological noise and the variability of measurements based on subjective responses. An auditory steady-state responses (ASSRs) procedure is explored as a technique which might overcome these limitations.


METHODS
Pure tone stimuli (500 and 1000 Hz), amplitude modulated at 40 Hz, are presented to 10 normal-hearing adults through headphones at three levels in 10 dB steps. Two conditions were assessed: unoccluded ear canal and occluded ear canal. ASSR amplitude data as a function of the stimulation level are linearized using least-square regressions. The "physiological attenuation" is then calculated as the average difference between the two measurements. The technical feasibility of measuring earplug attenuation is demonstrated for the group average attenuation across subjects.


RESULTS
No significant statistical difference is found between the average REAT attenuation and the average ASSR-based attenuation.


CONCLUSIONS
Feasibility is not yet demonstrated for individual subjects since differences between the estimates occurred for some subjects.
Department of Mechanical Engineering, École de technologie supérieure, Université du Québec, Montréal, Québec, Canada.
Olivier
O
Valentin
Rotman Research Institute of Baycrest Centre, University of Toronto, Toronto, Ontario; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
Sasha M
SM
John
Department of Mechanical Engineering, École de technologie supérieure, Université du Québec, Montréal, Québec, Canada.
Frédéric
F
Laville
D000328:Adult; D001301:Audiometry, Pure-Tone / Q000379:methods*; D004430:Ear Protective Devices / Q000592:standards*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D055815:Young Adult