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I am trying to record real-world sounds for hearing aid testing and am
wondering if anyone can help me out.
Specifically, I used a manikin (KEMAR) and the G.R.A.S. RA0045 ear
simulator to record street noises. The recorded sound will be presented to
subjects in the lab via earphones. My goal is to accurately replicate the
sound (especially in sound level) so that the listener is seemingly placed
on the street.
These are what I did.
1. Record the street sound (let’s call this sound is Input A) using the
KEMAR and the RA0045. The KEMAR’s ears are not occluded. The recorded
sound is called Output A.
2. Process Output A (e.g., filtering). Let’s call the processed Output A as
3. Present Input B to the KEMAR through earphones (Sennheiser IE 8 ear-
canal headphones), which are inserted into KEMAR’s ears. Record the sound
using the same RA0045. The recorded sound is Output B.
4. Compare Output B to Output A. Repeat steps 2 and 3 until a filter bank
that makes Output A and Output B have the same level and spectrum is found.
5. Use this filter bank to process Output A and present it to subjects.
I think these procedures could make earphones transparent because the
coupler microphone generates the same output for sounds from the street and
for sounds from the earphone.
However, when I was listening to the processed sound through the earphones
(step 5), my perception was that the sound delivered from the earphones was
louder than the sound that I heard on the street. Any comments? Thanks in
University of Iowa