The Cellphone and the Hearing Aid: The Odd Couple

When the FCC classified cellphones as essential forms of telecommunication in 2003, it made them subject to the 1988 Hearing Aid Compatibility Act. Oscar and Felix had to start getting along. Landline phones and hearing aids worked together fairly well from the beginning; they don’t emit RF energy, and they don’t contain as many sources of low-frequency emissions as cellphones do. In addition, thanks to the large size of these devices, manufacturers can install an additional telecoil transmitter for direct communication with the telecoil, a spool of wire that responds to a changing magnetic field, in hearing aids.

The ANSI ASC C63 standards committee, established in the 1930s to deal with the general issue of measuring and controlling electromagnetic emissions from all sorts of electronic equipment, published the first hearing-aid compatibility standard (ANSI C63.19) in 2001. The committee has since revised it twice, most recently in 2007. The standard describes limits and test procedures that address the need to control electromagnetic immunity (resistance to interference) in hearing aids and electromagnetic emissions in cellphones, and establish acceptable levels of background noise for hearing-aid users.

The current version of ANSI C63.19 describes methods to assign each cellphone an M (acoustic) and T (telecoil) rating for its emissions. A user can expect a normal level of compatible operation from a cellphone with a rating of M3/T3. For most hearing-aid users, that would mean hearing some background noise, but not enough to be annoying during a call of moderate length. An M4/T4 rating would correspond to excellent performance and no background noise for the majority of users.

The FCC currently requires cellphone manufacturers and network operators to certify that a significant portion of their handsets that operate using CDMA, GSM, iDEN, or 3G signals earn the ANSI C63.19 standard rating of M3/T3 or higher.

Over on the hearing-aid side, however, the situation is less clear. While the ANSI standard includes a test method and rating system for electromagnetic immunity, the U.S. Food and Drug Administration (FDA) does not currently require hearing-aid manufacturers to comply with these limits, although some hearing-aid manufacturers have begun voluntary labeling. Generally, the immunity of hearing aids on the market today is at a level of M2 or M3; that is, they can work with an M3-rated cellphone handset in a way that is not annoying. Hearing-aid users who purchase cellphones in retail stores can look for the hearing-aid-compatible rating and test them on the spot.

That’s not the end of the story, however. Wireless technology is a rapidly moving target, often outpacing the standards and regulatory processes. For example, Wi-Fi came quickly to the cellphone world, being implemented on handsets before standards bodies could revise the standard governing hearing-aid compatibility to take Wi-Fi into account. On the horizon, a number of other emerging wireless signals may soon be common on cellphone handsets to support broadband (WiMax, Long-Term Evolution), short range (Ultra-Wideband, ZigBee), and other forms of communication. Standards makers must be ever vigilant to keep pace with this rapid evolution of technology to save hearing-aid users from being shut out of a wireless world.