An individual head, auricle, and ear canal can alter signals from a hearing aid other sources of acoustic stimulation compared to artificial couplers. The most realistic method for quantifying or verifying certain parameters of acoustic simulation delivered to the ear by a hearing aid is to measure the sound pressure level of a signal in the ear canal of an individual while wearing an aid. Probe microphone measurements have been conducted and reported for the past 33 years. Until now, such microphone measurements have used a hollow tube inserted into the ear canal which leads to a transducer outside the canal. This paper describes our preliminary clinical application of a new wide range, flat response, miniature electret microphone, measuring 4 x 5 x 2 mm for measurement of insertion gain in a patient's ear canal. We believe the information from these recordings can be useful in developing objective clinical procedures for the selection and monitoring of wearable amplification for hearing-impaired patients.