Hearing aid electromagnetic interference from digital wireless telephones.
Several in-the-ear (ITE) and behind-the-ear (BTE) hearing aids were tested for audible interference at various distances from five types of digital wireless telephones. The interference which takes the form of a buzzing and a static sound was quantified using a calibrated system including a frequency analyzer and a pressure field microphone. The output of the each hearing aid was coupled to the microphone via Tygon tubing and a standard 2 cc coupler. The highest interference-induced sound pressure level (SPL), 122.5 dB, was measured from a BTE hearing aid placed within 2 cm of a transmitting Global System for Mobile Communications (GSM) phone. In this case, interference was detected up to a separation distance of almost 3 m. While all phones tested produced a similar interference level within 2 cm of this hearing aid, interference SPL from the code division multiple access (CDMA)-based system decreased more rapidly with distance than the time division multiple access (TDMA)-based phones tested.
Skopec
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Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD 20852, USA.
D055590:Electromagnetic Phenomena; D004867:Equipment Design; D006310:Hearing Aids; D006801:Humans; D013689:Telephone