Probe measurement of eardrum SPL in occluded real ears

Previously, we reported results from simulator studies of techniques for remote measurement of eardrum SPL in hearing aid occluded ears. These data provided means for calibrating remote-measuring probes which included the effects of ear canal length and impedance at the eardrum. The present paper presents data with respect to the accuracy of probe/earmold measurements of eardrum SPL in real ears. Measurements were made on fresh cadaver ears in which the eardrum SPL was independently measured with a micro-miniature microphone placed adjacent to the eardrum. Simulator-derived corrections obtained from the previous study were applied to the probe/earmold measuring system to compensate for ear canal length and assumed eardrum impedance. Results from several ears showed the wide variation associated with individual ear measurements and corrected probe/earmold errors of less than ± 4 dB for frequencies up to 6.0 kHz.