Benefit of a digital feedback suppression system for acoustical telephone communication.

Because hearing instruments have traditionally performed poorly during acoustical telephone use, the benefit of using a Digital Feedback Suppression (DFS) system for acoustical telephone communication was evaluated. For this purpose a special speech test based on the method and material of the Oldenburg Sentence Test was developed, presenting the speech signal via a telephone receiver. The correct coupling of the receiver and the hearing aid was monitored by means of a probe microphone. The word score was determined for two different settings of the hearing aid: (1) DFS activated (2) DFS deactivated. The difference in word score between these two conditions is an indication of the benefit provided by the DFS system. For almost all subjects, speech recognition at the telephone could be improved using the DFS system. This is a significant contribution in increasing end-user overall satisfaction with hearing aids.