Hearing Aid Frequency Response Test Sequence
This sequence follows the ANSI S3.22-1996 standard method for testing the frequency response of a hearing aid
Introduction
This sequence follows the ANSI S3.22-1996 standard method for testing the frequency response of a hearing aid. An equalized stepped sine sweep from 8 kHz – 200 Hz is played at a level of 60 dBSPL through the anechoic box speaker, and the output of the hearing aid is analyzed with the Heterodyne algorithm to produce a frequency response. Next, the HFA (High Frequency Average) is calculated by averaging the response values at three frequencies (1000, 1600, 2500 Hz). The HFA is then subtracted by 20 dB. Two post processing steps are used to find the upper and lower frequency points at which the response curve intersects this calculated value (HFA – 20 dB). These are the high and low frequency cutoff points.
Limits are set around these cutoff values, which represent the frequency range of the hearing aid. A third limit step is applied to the overall frequency response in accordance with the standard. A set of limits are included in the sequence, but these would need to be adapted to each individual device model. For more information, see section 6.10 of the standard.
Required Hardware
- Audio Interface – Listen AudioConnect or similar
- Power Amp – Listen SCAmp or similar
- DC Power Source – Listen DCConnect or similar
- Anechoic Test Box – Bruel & Kjaer 4232 or similar
- 2 cc Coupler – Bruel & Kjaer 4946 or similar
- ½” Reference Mic – B&K 4192 or similar
Setup Diagram
Hardware Setup and Calibration
- Calibrate the anechoic test box speaker as instructed in the SoundCheck manual.
- Calibrate the reference microphone in the coupler as instructed in the SoundCheck manual.
- Connect output 1 of your audio interface to the input of the amplifier powering the anechoic test box.
- Position your device inside the coupler, and place them at the reference point inside the anechoic test box. Connect the coupler to your microphone power supply.
- Connect the output of the mic supply to input 1 of your audio interface.
Get Sequence
This sequence is included in the Sequences folder of your SoundCheck installation.
