PROJECT SUMMARY
When programming a hearing aid, the amount of amplification necessary is adjusted to account for the
patient’s natural amount of external-ear amplification (EEA), provided by structures such as the pinna, concha,
and ear canal. Although two patients may exhibit identical, inner-ear hearing organ sensitivity (i.e. identical
severity of hearing loss indicated by their audiograms), their hearing aid amplification may be programmed
very differently, as their EEA can vary significantly depending on the unique shape and size of the external ear.
For example, smaller patients have smaller earcanals and exhibit higher EEA, because sound pressure level
increases as the space in which it resides decreases; thus, these patients require less hearing aid
amplification. Although norms exist for average-EEA in individuals age 1mo - adulthood (defined as >15 yr),
the best practice guideline is for audiologists to directly measure their patient’s individual EEA using
specialized probe-microphone equipment. Despite this gold-standard measurement method, 60-80% of
audiologists still use an automated, average-EEA estimate when programming hearing aid amplification,
because it saves time and money, even though it can yield amplification errors up to 20 dB. This significant
amount of error is likely to result in either poor audibility from under-amplification, or noise-induced hearing
injury from over-amplification, in addition to considerable dissatisfaction with the hearing aid. A major source of
error in the current, average-EEA predictions is that they are based on chronological age, around which there
is high variability in human body size (including the size and shape of the external-ear responsible) at
all stages of pediatric development, and in fully grown adulthood. Therefore, we believe that predictions
of average-EEA could be improved by using body height as the proxy measurement of EEA, instead of body
age. Updated and improved average-EEA predictions should be used in automated hearing aid programming
in both audiologist-fit hearing-aids and over-the-counter hearing aids, in order to reduce major amplification
errors, thereby improving hearing aid safety and audibility. We will test the hypotheses that 1) average
real-ear-to-coupler difference measurement predictions (a type of EEA measurement for hearing aids coupled
to earmolds) based on body height will yield statistically significant and clinically relevant accuracy
improvement over the current predictions based on body age, and 2) real-ear-unaided-gain (a type of EEA
measurement for hearing aids coupled to receiver wires and perforated domes) and body height will exhibit a
statistically significant correlation, thereby establishing new, normative data for use in open-fit hearing aid
programming. These analyses will be conducted in two cohorts; Specific Aim 1 will test these hypotheses in
the adult cohort (> 18 yr); body height, age, pinna size, and EEA will be analyzed cross-sectionally. Specific
Aim 2 will test these hypotheses in a pediatric/adolescent cohort (3 mo-15 yr); age, body height, pinna size, ear
canal size, and EEA will be analyzed using an accelerated, 4 yr longitudinal design.
