REAL-EAR TO COUPLER DIFFERENCES IN CHILDREN WITH GROMMETS

Real-ear to coupler differences (RECDs) are important for the selectio n of appropriate amplification characteristics for hearing impaired ch ildren. The aim of this study was to investigate the effects of patent grommets on RECDs in children. Subjects were 32 children aged between 4 and 7 years, 16 had a patent grommet in one or both ears as confirm ed by otoscopy and large equivalent ear canal volumes on tympanometry. There was no evidence of middle ear pathology in the remaining 16 who comprised the control group. All real-ear and coupler measures showed good test-retest repeatability across the whole frequency range. The mean difference in RECDs between the two groups in the frequency range 0.125-0.75 kHz was 15 dB. The differences in RECDs were statistically significant (P < 0.01) for all frequencies below 0.75 kHz. There was a strong correlation between the mean RECD and equivalent ear canal vo lume at all frequencies between 0.125 and 0.5 kHz, and a moderate corr elation at 0.75 kHz. Large inter-subject variability was found, with a maximum standard deviation of 6.6 dB at 4.0 kHz. Therefore, this stud y supports the need for individual RECD measures to be made, particula rly for subjects with grommets, rather than using averaged transformat ion figures. It suggests that more low frequency gain should be given to hearing aid users with patent grommets to overcome the reduced SPL in the ear canal, due to leakage through the vented tympanic membrane.