Acceptable level of acoustic disturbances to speech signal as a measure of successful hearing aid fitting
Dorota Hojan-Jezierska, Edward Hojan, Magdalena Pankowska, Marlena Gauza, Dariusz Wlodarczyk
JHS 2011; 1(3): EA80-82
A method has been established to measure the maximum acceptable background noise level (BNL) for a listener, while listen¬ing to speech at the most comfortable listening level (MCL). The acceptable noise level (ANL) is the difference between BNL and MCL.
The ANL procedure was used to measure acceptance of noise in the presence of speech at MCL, that was stated as 65 dB for normal-hearing listeners. There were two groups of normal-hearing listeners treated in two ways.
In the first stage of the study, a group of 16 students were exposed to the list of words at the lev¬el of 65 dB SPL (MCL). The level of “babble” noise was increased up to the moment when the person declared discomfort. At such level of “babble” noise (BNLX%) the acceptable noise level ANLX%, and the speech intelligibility X% were determined.
The aim of the second stage of experiment (for a group of 36 students) was to establish a level of “babble” noise BNLX% (and then the acceptable noise level ANLX%,) at the level of speech intelligibility X% determined in the first task.
It was found that the X% determined at the state of discomfort equals 61% for ANL=(19±2) dB. The ANL estimated at the X%=61% is very similar and equals (18±2) dB.
Keywords: Hearing Aids, Speech Perception, Speech Intelligibility