A Developement of A New Test Procedure for An Induction Pick Up Coil Sensitivity

Abstract

It is dificult to understand a sensitivity and a frequency response of a pick up coil by IEC 118-1 procedure, and to recognize the differences between ‘M’ and ‘T’ position. These problems are caused probably by the inaccurate data of the pick up coil's sensitivity tested at a maximum gain control in the low inductive signal.
The author developed an easy and effective test procedure to solve these problems by avoiding many kind of noises. A variable magnetic field test loop system is also assembled for ‘high S/N analizing’. It became possible to us that the accurate and understandable data for analysis, and the usefulness to culculate the out put sound pressure level from a hearing aid used in the loop system. Further, the diferences of hearing aid's frequency responses between ‘M’ and ‘T’ position were shown clearly. The weakpoints of the latest loop systems also became clear in bringing clear sounds for hearing aid users.