DIGITAL FEEDBACK SUPPRESSION (DFS) - CHARACTERIZATION OF FEEDBACK-MARGIN IMPROVEMENTS IN A DFS HEARING INSTRUMENT

The introduction of a new power behind-the-ear hearing instrument equi pped with an integrated digital feedback suppression (DFS) system, bas ed on adaptive, digital signal processing, creates the need for new me thods for evaluating the characteristics of this new technology. A spe cial measuring method based on determination of the complex loop gain of the DFS instrument and the associated feedback path is described. T his method yields information about the static feedback-margin improve ment due to the DFS system, and the method is usable especially in con nection with measurements on real ears. It requires fairly advanced te st facilities, including a dual-channel FFT analyzer and, by preferenc e, an anechoic room. Loop gain measurements on the new DFS power behin d-the-ear hearing instrument show encouraging results. Groups of profo undly hearing-impaired children and adults were tested, and static fee dback-margin improvements in the order of 10 dB for the new DFS power hearing instrument were seen. Variations were largest for groups using own ear moulds and individually fitted instruments.