First Advisor

Douglas Martin

Term of Graduation

Winter 2000

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Speech Communication: Speech and Hearing Sciences


Speech Communication




Audiology, Hearing aids for children



Physical Description

1 online resource (iii, 51 pages)


Because there are many variables and much missing information when fitting young children with hearing instruments, it is necessary to rely on prescriptive procedures such as the Desired Sensation Level (DSL) Method to create target 2cc gain values for ordering and fitting hearing instruments. Inherent in creating 2cc targets is a conversion process known as a real-ear to coupler difference (RECD) measurement. The DSL algorithms make allowances for averaged data to be used in lieu of this measurement.

The purpose of this study is to evaluate the validity of using averaged real-ear to coupler difference values included in the DSL computer program in its calculation of target 2cc coupler gain for hearing instruments. The results of applying those values when fitting hearing instruments, as opposed to using custom values, was determined. To achieve a measure of the impact of any observed deviation from the DSL's RECD values, both custom RECD values and the averaged values used by the DSL Program were used to predict real-ear response curves from measurements of each subject's hearing instrument(s) on a 2cc coupler.

RECD values were calculated for twelve children (twenty ears} with normal outer ears and intact tympanic membranes, as determine by the researcher. These values were compared against published values and analyzed for inter-subject variability.

Analysis of the data demonstrated a wide variability of RECD values between subjects, even though the average of all ears reasonably approximated published averaged data. When individual RECDs were used to create 2cc targets, it was discovered that there is potential for targets generated using average data to significantly over-amplify some patients and under-amplify others.


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