Hearing Aid Research
- Phase IIIA: Study of the Interaction of Wireless Phones and Hearing Aids
- Compare acoustic measurements of the interference between various combinations of wireless phones and hearing aids to the usability classification predicted by the C63.19 Hearing Aid - Wireless Phone Compatibility Standard.
- - 8 Hearing Aids (ranging from low to high immunity)
- - 10 Wireless Phones (CDMA, TDMA-50 Hz, TDMA-217 Hz at 800 and 1900 MHz)
- - 5 Power Levels (0, 6, 12, 18, and 24 dBm)
Hearing Aid Phase IIIA: Objective Validation Study
The eight hearing aids and ten wireless phones were tested in combination (eighty test runs) at each of five power levels (nominally 0, 6, 12, 18, and 24 dBm) to examine the overall impact of immunity, maximum emissions, and power level on acoustic interference. Tests were conducted at a 1 cm separation distance between the aid and phone in a sound isolation chamber using the standard test equipment (acoustic spectrum analyzer, pressure microphone, 2cc coupler, and Tygon tubing). The interference output spectrum was converted to an Input Referenced Interference Spectrum by removing the hearing aid frequency response and the Overall Input Referenced Interference Level was computed.
There were five statistically significant groupings of hearing aids ranging from high to low immunity. These groupings showed good correspondence with the TUV data. Differences in interference among the different phones showed less correspondence to E-field and H-field emission levels. In general, the data lend support to the C63.19 philosophy, but point out that some issues must still be resolved in order to improve the accuracy of the categorization scheme which is used to predict performance of a specific hearing aid-wireless phone combination. The construction of an appropriate model of interference that can be used to further evaluate the data is nearing completion.