Comparison of measurements of the characteristics of directional microphone hearing aids in an IAC test room and an anechoic chamber.

The purpose of this study was to assess the possibility of measuring directional microphone hearing aids (DMHAs) using standard hearing aid test instruments in a sound field environment. The use of DMHAs is increasing and research has shown that under certain difficult listening situations, superior results are obtained by hearing impaired individuals with directional versus omnidirectional microphone arrangements. However, valid electroacoustic evaluation of the DMHAs cannot be accomplished using the conventional hearing aid test box. The ideal environment for such evaluations is an anechoic chamber, a facility not found in most audiological clinics. Results show that if the proper precautions are observed, the electroacoustic characteristics of DMHAs can be measured in a sound field environment using conventional hearing aid test instrumentation. Validation of this procedure was carried out by comparing sound field results with those obtained in an anechoic chamber.