To compare gain values acquired through probe mic measurements with those obtained with a 2 cc coupler and determine the articulation index.

Procedure:

Use a mild gain aid (FOG < 40) set to its mildest settings. Use the Knowles Electronic Mannequin for Acoustic Research (KEMAR) with its custom mold. First measure ear canal resonance (REUR). Then fit the hearing aid and adjust the volume control to a tolerable setting. Then measure in situ gain (REAR). Determine insertion gain (REIG). With the volume control in the same position, measure 2 cc coupler gain using the same input level.

Writeup:

1. Cut, paste, and label COMPLETELY the following (include hearing aid settings:

a. ear canal resonance

b. in situ gain

c. insertion gain

d. 2 cc gain for that volume setting

2. Discuss the following comparisons

a. insertion gain across the frequencies

b. the difference between insertion gain and 2 cc coupler gain

c. the difference between insertion gain and corrected 2 cc coupler gain (use Hawkins' values for closed mold)

3. Given the observed insertion gain and the count-the-dot audiogram, calculate the articulation index for a person with

a. a flat, 40 dB HL loss

b. a flat, 60 dB HL loss