The fitting of hearing aids with in situ measurements

The implementation and utilization of in situ Real-Ear Measurements (REM) gives the hearing care professional an objective, reproduceable, and quantitative tool to use with the fitting of the hearing instrument(s) or amplifying devices. One of the many applications of REM is in the programming of a hearing aid for a child. If the hearing health care professional only references the measurements provided by the manufacturer, (typically acquired with a coupler without taking account of the measurements in situ), there would be the risk of an excessive amplification of sounds at the eardrum. This is based on the notion that the ear canal volume of a pediatric patient is smaller than an adult ear canal volume. If one presents the same intensity of a signal, the sound pressure generated in a small cavity is greater than the one generated in a cavity of larger volume.

A REM (Real-Ear Measurement) system allows the practitioner to accurately measure the performance of an amplifying device directly in the patient's ear canal. The acquired measurement shows the real sound pressure level (intensity) produced by the hearing aid at the patient's eardrum and allows the practitioner to adjust the gain of the hearing aid to meet the patient’s needs. The time required to carry out an in situ measurement is fully rewarded in terms of quality of fitting, enhances the acceptance of the hearing aid by the patient and reduces follow-up time. Another advantage of a REM system involves the area of counselling. During the measurement session it gives the patient and third party a visual representation of how the amplifying device is affecting the patient’s audibility.

Considering the advantages that a REM system offers; it is therefore clear how this type of approach should be adopted when both the selection and the fitting of a hearing aid are performed, as well as during the subsequent sessions of follow-up.