Hearing aids have not in the past always worked effectively with mobile phones, because of electronic interference between the 2 devices that caused static, whistling or squealing noises, or lost words. New government regulations, together with considerable advances in both phone and hearing aid technology, have made this incompatibility uncommon. The labeling requirements mandated by the new government regulations make it easy to find a mobile phone that is compatible with your hearing aid.
Understanding the rating system requires a bit of knowledge about the modes that hearing aids can operate in. There is an M mode (which stands for microphone) and a T mode (which stands for telecoil). In M mode, your hearing aid uses its built-in microphone to pick up audible sounds from the environment and amplify them so that you can hear them. In T mode, the hearing aid uses telecoil technology instead. The hearing aid is able to pick up the electromagnetic signals from inside the phone directly. Currently, approximately 60% of hearing aids sold in the US have a telecoil or T mode.
Under the new regulations, these two modes of operation have ratings that range from 1 (the lowest sensitivity) to 4 (the highest sensitivity). To be labeled as hearing aid compatible (HAC) a cell phone must carry a minimum rating of M3 or T3.
Hearing aids and cochlear implants have a similar M and T rating system to certify how sensitive they are in each mode, and how resistant they are to radio frequency interference. If you know the M and T ratings for your hearing aid, to determine its compatibility with any mobile phone, just add the two sets of ratings together. A sum of 6 or more makes a solid pairing. That hearing aid and mobile phone combination should work well for you. If the combined rating is 5, this combination is considered normal and suitable for most regular phone use. A combined rating of 4 is considered usable for brief calls, but may not be suitable for extended phone use.
This combined rating system makes it easy to shop for a mobile phone online, because it easily allows you to determine how compatible it will be with your hearing aid. A better approach, of course, would be to go to a store that allows you to “try before you buy,” and actually use the phone you want while wearing your hearing aid, in both M and T modes.