SS01: NOISE REDUCTION IN HEARINGS AIDS AND ITS EVALUATION

ADVANCED DIGITAL NOISE REDUCTION

Eric Branda

Siemens Audiological Engineering Group, Erlangen, Germany.

It is generally accepted that a common concern among hearing instrument wearers is the use of amplification in noisy environments.  The various types of noise as well as loudness levels can impact the amount of annoyance perceived by the hearing instrument wearer.  It has also been supported that the basic skill required for speech understanding in noise is "auditory stream segregation" (Bregman 1990), which refers to the capability to sort environmental sounds and identify their original sources. 

With the growth of digital hearing instruments over the past several years, algorithms to address the noise issue have grown as well.  Advanced digital noise reduction (DNR) techniques have become more or less “standard” in today’s hearing aids.  The methods of detection and implementation can vary for diverse types of noise.

However, even advanced DNR techniques do not separate speech from noise, but rather reduce noise when noise is dominant. These implementations are generally found not to increase intelligibility in noise, but to help increase the listening comfort in noise.  Additionally, DNR might be capable of supporting auditory stream segregation and thus, improve ease-of-listening and decrease cognitive effort for speech perception.

An understanding of the behavior of DNR in hearing instruments can help the practicing clinician in adjustment of the hearing instruments as well as in counseling the hearing instrument wearer.  This presentation will focus primarily on the technical principles of noise reduction techniques as used in hearing aids.