Hearing aids have not in the past always worked well with mobile phones, because of electronic interference between the two devices that triggered static, whistling or screeching noises, or dropped words. Technology improvements along with new government regulations have largely eliminated this problem. Nowadays cell phone – hearing aid compatibility isn’t the huge problem it used to be. 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). When your hearing aid is in M mode, it uses the built-in microphone to pick up audible sounds from around you and amplify them to make them easier for you to hear. When the hearing aid is in T mode, instead of the microphone it uses its built-in telecoil to directly pick up conversations from inside the phone, in the form of electromagnetic signals. Roughly 60 percent of all mobile phones sold in the U.S. have a telecoil (T) mode.

The rating system for these two modes of hearing aid operation uses a scale that ranges from the lowest sensitivity (1) to the highest sensitivity (4). No mobile phone or cordless handset sold in the United States can be sold as hearing aid compatible (HAC) unless it has a rating of at least 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. A combined rating of 5 is thought of as normal, and suitable for most people. A combined rating of 4 is considered usable for brief calls, but may not be suitable for extended phone use.

Since being introduced, the new rating system has made it much easier to shop for a cell phone online and determine its compatibility with your hearing aid in advance. 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.