A New System for the Individual Fitting of Hearing Aid

In spite of many improvements of hearing aid, the fitting manuals are not yet feasible and each hearing handicapped patients still need particular consideration. And the authors found that shape of audiogram does not always indicate the particular need for a patient, and also speech audiometory may not be helpful in some cases. “A Master Auditory Trainer-MAT” developed three years ago by the authors has adjustable gain 6 band step octave filters and it was caliblated accurately in the sound pressure level, and also contained the ARCs (compression devices). Although the MAT was specially designed for the diagonistic and the auditory training use. And it has been used efficiently to determine the type of hearing aid to meet the individual needs, the authors found some difficulties to apply the MAT's data to hearing aid directly. The difficulties seemed to be due to different circuits and voltage used. Therefore, two different instruments, with same circuits, controls and operating voltage were developed. One of them was called “Hearing Aid Fitting Tester-HK”, which was contained in a desk type metal cabinet, and the other was called “HA-X”, which was built in a small body aid box. In these matched-pair instruments, there were two easy contorolable band filters with a cross-over point, at 750Hz, which could devid the speech frequency range into two parts. With the same handling of MAT, we could easily find the best point in the controls of HK within a few minutes with live or running voice test. And many of our clients much satisfied in fitting their hearing aids with this combination even if they have ordinary aids. With two HKs in a stereophonic training unit and, in a good individual fitting type training unit of the group hearing aid, a new system is nearly accomplished.