Investigation of Interaction Between CDMA Wireless Phones and Hearing Aids
[Order Report] [Executive Summary]
The EMC Center conducted a study for the CDMA Development Group (CDG) investigating potential solutions to minimize the interaction between CDMA wireless digital phones and hearing aids.
The CDG study consisted of testing nine hearing aids with four CDMA phones from two manufacturers. Each manufacturer provided one phone that operated in the 800 MHz frequency band, and a second phone that used the 1900 MHz band.
The focus of the study was to investigate the effects of various phone puncture rates and transmission power levels with the objective of determining the power level at which interference becomes unacceptable.
This threshold could be used to trigger the phone to switch to a full puncture rate, thereby reducing the interference and increasing the phone's usability by hearing aid wearers.
To obtain a conservative estimate of the
interference threshold, three
Behind-the-Ear (BTE) hearing aids and three In-the-Ear (ITE) hearing aids
that exhibited substantial interference (poorest immunity) in Phase II-C
of the EMC Center's Hearing Aid- Wireless Phone Study were selected for
testing in the CDG's study. Three additional ITE aids with better
immunity were chosen to balance the study.
Figure 1: Percentage of Tested Hearing Aids Failing to Comply with Specified Interference Level as a Function of Puncture Rate and Phone Power Level for All Phones Combined.
