Abstract
127 patients fitted with CROS and Bi-CROS hearing aids during the years 1967–72 at the State Hearing Centre, Aarhus were questioned about the results. It was discouraging that among the patients with normal hearing in the good ear (group 1) only 20% used the hearing aid regularly, whereas the patients with varying degrees of hearing loss in the good ear seemed to accept the hearing aids more readily (groups 2–3). The problems of the fittings have been investigated, and it was found that the tube diameter was the critical factor. The importance of modifying the tube diameter to hearing loss has been illustrated in experiments on IROS, CROS, Mini-CROS and Focal-CROS. Standard tubes (2 mm) give noise problems in patients having normal hearing in the good ear, whereas smaller tubes (1.2–1.4 mm) amplify only the high frequencies necessary for discrimination of particular consonants and are thus tolerated better. An examination of 40 patients fitted according to this principle showed that 77.5% were satisfied.