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Auditory brainstem responses to chirps delivered by different insert earphones
Claus Elberling1, Sinnet G B Kristensen, Manuel Don
1William Demant Holding A/S, Kongebakken 9, DK-2765 Smørum, Denmark. ce@demant.dk
The Journal of the Acoustical Society of America
|March 20, 2012
Summary
The ER-2 earphone shows larger auditory brainstem responses (ABRs) for chirps than the ER-3A, due to its broader frequency response, not smoother group delay. This impacts hearing assessment research.
Area of Science:
- Audiology
- Biomedical Engineering
- Neuroscience
Background:
- Accurate auditory evoked potential measurements rely on precise earphone frequency response and sensitivity.
- Standardized ear simulators can introduce artifacts, potentially affecting measurement validity.
- ER-3A and ER-2 earphones are commonly used for auditory brainstem response (ABR) testing.
Purpose of the Study:
- To compare the frequency response and sensitivity of ER-3A and ER-2 earphones using different ear canal extensions.
- To evaluate the impact of these earphones on auditory brainstem response (ABR) recordings.
- To determine the factors contributing to differences in chirp-evoked ABR amplitudes.
Main Methods:
- Frequency response and sensitivity measurements of ER-3A and ER-2 earphones in an occluded-ear simulator with three ear canal extensions.
- Recording auditory brainstem responses (ABRs) using both earphones with chirps and clicks in 22 normal-hearing individuals.
- Simulating ER-3A amplitude response with ER-2 group delay to isolate the cause of amplitude differences.
Main Results:
- The standard DB 0370 ear canal extension introduced a resonance peak around 4500 Hz, unlike other extensions.
- ER-3A exhibited a band-pass filter-like amplitude response and rippled group delay, while ER-2 showed flat, smooth responses up to 10000 Hz.
- Chirp-evoked ABRs were significantly larger with the ER-2 earphone at lower presentation levels (<60 dB nHL), while click-evoked ABRs showed only a slight difference.
Conclusions:
- The ER-2 earphone's broader amplitude response, not its smoother group delay, is responsible for the increased chirp-ABR amplitude.
- Earphone characteristics significantly influence ABR measurements, particularly for chirp stimuli.
- Careful consideration of earphone frequency response is crucial for accurate interpretation of ABR results.
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