Effect of reference microphone location and loudspeaker azimuth on probe tube microphone measurements

The effects of loudspeaker azimuth and reference microphone location on probe tube microphone measures were assessed. The real ear unaided response (REUR), real ear aided response (REAR), and real ear insertion response (REIR) were obtained on a KEMAR. Aided measures were obtained with both a behind-the-ear and an in-the-ear hearing aid. All three measurements were affected by changes in the loudspeaker azimuth and reference microphone location. Responses obtained with a 90 degree loudspeaker azimuth or with the reference microphone located at-the-ear revealed greater disparity than those obtained under other conditions. Most of the differences occurred at frequencies above 2000 Hz, with measurements utilizing the behind-the-ear hearing aid showing greater dispersion. These results suggest that the location of the loudspeaker and the reference microphone are important variables when utilizing probe tube microphone measurements.