Real Ear to Coupler Differences in Children and The Effects of Hearing and Microphone Location

The early identification of hearing loss and selection of appropriate amplification are the most important goals for children with hearing impairment. Selection of appropriate amplification for a pediatric population involves maximizing the hearing impaired child\u27s residual hearing, for development of speech and language. In addition, it is important to consider the acoustic differences between the 2 cc coupler versus the real ear. During the hearing aid selection process, it is customary to predict how a hearing aid will respond in the real ear, based upon a given 2 cc coupler response. Killion and Monser (1980) developed a formula for converting the 2 cc coupler response of a hearing aid to a real ear insertion response, or conversely, a real ear insertion response to a 2 cc coupler response. This formula was designed to account for the real ear to coupler difference and the effects of hearing aid microphone location. A body of standardized corrections for the real ear to coupler difference and hearing aid microphone location effects is available. However, due to errors which may be introduced when utilizing standardized corrections, several researchers have recommended the use of individualized corrections. The primary purpose of the present study was to quantify real ear to coupler differences in a pediatric group, and evaluate a technique for deriving hearing aid microphone location effects in hearing impaired children. The real ear to coupler difference was measured in ten children and the hearing aid microphone location effects were measured for fourteen behind-the-ear hearing aids. Results demonstrated that the RECD was statistically significant and increased as a function of frequency. Large individual variation in the RECD was noted, particularly in the high frequencies. These results demonstrate the limitations of the 2 cc coupler in predicting the real ear response. The hearing aid microphone location effect results revealed large negative values and large intersubject variability. Inspection of these data, indicate little consistency with other published studies. The RECD and hearing aid microphone location effect results indicate that corrections are necessary when selecting amplification for children. The implications of using standardized versus individualized corrections are discussed for the RECD and aid microphone effect