Electroacoustic characteristics of personal FM systems.

Electroacoustic characteristics of various personal FM system configurations were obtained through the use of a Zwislocki ear simulator and KEMAR. Saturation Sound Pressure Level 90 and frequency response curves were obtained with different hearing aids in the microphone mode and then compared to the response obtained when the hearing aids were coupled to a FM receiver via neck loops and direct input. In addition, hearing aid orientation to and distance from the loop, clothing effects, internal noise levels, FM receiver volume control taper, and the effect of different FM receivers were investigated. The results indicated substantial microphone-teleloop response differences. Only minor differences were observed in the microphone-direct input comparison. Other variables were found that significantly affect the use of these personal FM systems. The results are discussed in terms of the implications for clinical use.