Comparison of Real-Ear to Coupler Difference Values in the Right and Left Ear of Adults Using Three Earmold Configurations

In Brief Objective: The purpose of the study was to compare real-ear to coupler difference (RECD) values in the right and left ear of adults using three earmold configurations. Design: The RECD was obtained from both ears of 18 normal hearing adults by subtracting the HA2 2-cc coupler response from the real-ear response using an ER-3A insert earphone and a swept pure tone on the Audioscan RM500 probe-tube microphone system. The measurements were made with a personal earmold, foam eartip, and oto-admittance tip. Results: The mean difference between the right and left RECD was close to 0 dB for all earmold configurations and was not statistically significant on a repeated-measures analysis of variance (p > 0.05). In 90% of participants, the difference between ears was generally less than 3 dB at 0.5 to 4 kHz. Conclusions: Cooperative participants with non-occluding wax and normal middle ear function (on tympanometry) show small differences in RECD between the right and left ear, irrespective of the earmold configuration. The study has yet to be extended to the clinical setting where subject cooperation and earmold fit may differ from the present study. In the meantime, the findings from the present study indicate that where an RECD can be obtained from only one ear of a participant, it is probably best to use this to derive real-ear SPL of both ears instead of relying on average age appropriate corrections. The high intersubject variability associated with real-ear to coupler difference (RECD) values means that it is advisable to measure these from each infant whenever possible. Although the test time is usually brief in cooperative subjects, it is not known if it is necessary to obtain the measurement from each ear. The similarity between the RECD values from the right and left ear was examined in a group of adults using different earmould configurations. The results show that the mean difference is close to 0 dB with a right/left difference less than 3 dB in most individuals. This suggests that it may be sufficient to measure the RECD from only one ear of a subject; however, the study has yet to be extended to the clinical setting where variability in subject cooperation and earmould fit may be higher.