Individualized Correction Factors in the Preselection of Hearing Aids

Abstract

This study investigated three issues involving corrections for individual ear acoustics in hearing aid prescriptions: (a) the extent to which inconsistencies in the sound-field reference position can affect comparative corrections for the real-ear unaided response (REUR); (b) the extent to which individual variability in the real-ear-to-coupler level difference (RECD) supports the use of individual measurements as opposed to an average-ear estimate; and (c) the adequacy of using KEMAR estimates of the effects of the location of the hearing aid microphone. In Experiment 1, KEMAR REURs using over-the-ear and under-the-ear reference positions were compared with KEMAR REURs using a center-of-head reference position. Maximum differences of 4–9 dB were found in the 1500- to 5000-Hz range, depending on test conditions. In Experiment 2, the ear canal response of an insert earphone was compared to the 2-cc coupler response of the same earphone to calculate the RECD. Individual RECDs for a population of hearing aid candidates were compared to the RECD for KEMAR. For 8 of the 15 subjects (9 of 18 ears), the RECD was more than 4 dB different from KEMAR at two or more third-octave frequencies between 500 and 4000 Hz. In Experiment 3, the effect of the location of the hearing aid microphone for in-the-ear (ITE) and in-the-canal (ITC) locations was compared with the over-the-ear (OTE) location for 18 ears and for KEMAR. The effects varied across individual ears, but all ears and KEMAR showed positive gain in the high frequencies for the ITE and ITC locations. The relevance of these results to hearing aid prescription practices is discussed.

Probe-Tube Microphone Measures in Patients with Open-Mastoid Surgery: Real-Ear-to-Coupler Differences and Real-Ear Unaided Responses

“…Our RECDs for the control group generally agree with the mean data from earlier studies [Sachs and Burkhard, 1972;Nelson Barlow et al, 1988;Feigin et al, 1989;Hawkins et al, 1990;Fikret-Pasa and Revit, 1992]. There is a general trend for RECDs to increase with increasing frequency in normal adults.…”

“…coupler', while REUR primarily refers to a measure of the resonance characteristics of the unoccluded external ear [Mueller, 1992]. Many previous researchers have measured the RECDs from normal and pathological ears [Sachs and Burkhard, 1972;Nelson Barlow et al, 1988;Feigin et al, 1989;Hawkins et al, 1990;Fikret-Pasa and Revit, 1992;Martin et el., 1996Martin et el., , 1997 middle ear acoustics, it can be hypothesized that RECDs in patients who undergo this kind of operation will differ from those in normal ears. Therefore, the aim of this study is to investigate the effects of open-mastoid surgery on RECDs in adults.…”

Real-Ear to Coupler Difference in Patients with Ear Drum Perforation

“…Previous studies [5][6][7][8] have all demonstrated a relatively large intersubject variability in RECD for both adults and children. Our results show that the variations among subjects in patients with ear drum perforation are much larger than those among normal controls, which demonstrates the apparent necessity to measure RECD individually in this kind of patients.…”

“…Also, little is known about the relationship between perforation size and RECD values. From the particular subject in the report by Fikret-Pasa and Revit [8] and the effect of grommets on RECD in children [10], it is possible that RECD in patients with ear drum perforation will differ from RECD in normal subjects. The purpose of this study is to investigate the effects of ear drum perforation on the RECD of adult subjects.…”

“…However, there have been very few studies investigating RECD in patients with middle ear pathology. Fikret-Pasa and Revit [8] measured RECDs from adults and presented data of 1 subject who had a perforated ear drum. The RECD response from this subject was notably different from that of the others, having a smaller RECD in the lower frequencies compared with other normal subjects.…”