Review of the Development of TIA-1083

Consumer Complaints In 2004, telephone manufacturers began to receive customer complaints regarding hearing aid interference problems with digital cordless telephones. Specifically consumers were hearing a buzz noise when using digital cordless telephones with hearing aids and cochlear implants when set to T-Coil mode. There were no reports of the buzz noise from analog cordless telephones.

Industry Response At the August 2004 meeting of TIA Subcommittee TR41.3 a Gallaudet University presentation on the subject was discussed along with possible causes for the reported interference. The consensus belief was that, due to the low RF power levels used by cordless phones, the source of the reported interference was probably magnetic. Further work towards confirming this belief and developing a testing method to characterize the magnetic interference was conducted during the remainder of 2004 and first half of 2005.

Industry Response First, the complaint phones were tested for compliance with the FCC Part HAC regulations. The test results confirmed that all of the phones were compliant. Next, the complaint phones were tested with hearing aids obtained from and programmed by Gallaudet University. This testing confirmed that digital spread spectrum cordless telephones were indeed causing interference to hearing aids. (This testing also confirmed that analog cordless telephones did not cause interference.)

Why was this happening? Analysis of the noise characteristics indicated that the source of the noise was the Time Division Duplexing (TDD) employed by the Digital Spread Spectrum (DSS) cordless phones to enable them to transmit and receive on the same frequency. This turning on and off of the transmitter at a very rapid rate resulted in large changes in battery current which in turn caused large changes in the magnetic field produced by the wiring in the handset. This magnetic pulsing was being picked up by the T-Coil in the hearing aid and heard as a loud buzzing noise by the wearer.

HLAA Studies 2005 HLAA National Convention Study conducted by Linda Kozma-Spytek of the Rehabilitation Engineering and Research Center (RERC) on Telecommunications Access and the Technology Access Program at Gallaudet University. Volunteers from among the HLAA Convention attendees tested a group of phones and rated their performance. – Loudness – Percent Words Understood – Interference – Usability – “Would you buy a phone with this level of interference?”

HLAA Studies 2006 HLAA National Convention Study conducted by Gallaudet University, Etymotic Research and Motorola. Volunteers from among the HLAA attendees participated in this study and helped to answer the question: “How much noise is too much noise?”

TIA Completes Development of New Standard Results from the two HLAA Studies were compared with lab measurements by TIA member companies. Performance Requirements were Established Compliant phones were tested by wearers of hearing aids and cochlear implants with good results. ANSI/TIA-1083 “Handset Magnetic Measurement Procedures and Performance Requirements” was published in March Official “TIA-1083” logo was developed and licensed by TIA to manufacturers for display on the packaging of compliant products.

Official TIA-1083 Logo Compliant products with this logo are currently widely available in the market.