NORMAN, Okla.-The first phase of University of Oklahoma research has concluded that different digital phone technologies can interfere with hearing aids, but researchers have yet to settle on how to resolve the problem.
“This clinical study is the most comprehensive scientific effort to date in the United States to involve a diverse group of hearing aid users to determine the degree of interaction between hearing aids and wireless phones,” said Ravi Ravindran, director of the University’s Center for the Study of Wireless Electromagnetic Compatibility.
Ravindran said the “study identified several factors that contribute to the interaction, and also demonstrated the complexity of the problem.”
Phase I of the University of Oklahoma study examined conditions producing the most extreme interaction to ascertain the maximum potential level of interference to hearing aids from cellular phones. Variables that affect the level of interaction include the technology, the type and configuration of hearing aid, the severity of hearing aid or a combination of factors.
In that setting, researchers found that hearing aid users generally did not experience interference unless phones were within 24 inches of the hearing aid user.
Behind-the-ear hearing aids with internal or external metallic coating were determined to be effective in curbing bystander interference at all distances.
While placing a metal shield between the phone antenna and hearing aid also reduced interference, researchers discovered that antenna shielding raises questions such as technical feasibility, manufacturability and quality of phone performance.
Phase I clinical trials used 68 hearing aid users and 10 non-hearing aid users, and lasted from December 1995 through March.
Phase II, which will examine phone interaction with hearing aids under normal circumstances, is underway.
The results are apt to be most disappointing to some Code Division Multiple Access proponents, who’ve claimed for months that CDMA technology developed by San Diego, Calif.-based Qualcomm Inc. does not cause interference to pocket phones and therefore should be more desirable to consumers than the other two technologies tested: PCS-1900 (Global System for Mobile communications and TDMA (Time Division Multiple Access) 800.
