Helen Connor Ph. D., Ballerup (Denmark)
“Comparison of hearing aid noise reduction using objective measures”
A common complaint with hearing aids is “my hearing aids are too noisy”. To improve listening comfort in background noise, most modern hearing aids offer single-microphone Digital Noise Reduction (DNR). Previous studies indicate that for some hearing aids, DNR can improve the subjective perception of background noise.
The current study investigated the regulation speed of hearing aid DNR. Recordings of the output of five premium hearing aids were made in the coupler in a test box with DNR off and on. The signals were unmodulated noise and speech in noise.
Results showed that for noise only, the different DNR algorithms had quite different attack times. To quantify how DNR is applied to speech in noise, the variation in short-term gain reduction across time was calculated. The fastest-acting DNR algorithms vary the gain the most for a speech-in-noise signal. This influences the modulation characteristics of the hearing aid output.
This study demonstrates how differently DNR in hearing aids can perform, and highlights the need to have a standardised benchmarking procedure.