Hearing aids have not previously always worked well with cellular phones, because of electronic interference between the two devices that caused static, whistling or squealing noises, or lost words. Thankfully, improvements in technology and new government regulations have made the issue “Will this phone work with my hearing aid?” easier to answer. The regulations mandated new labeling requirements and ratings that help you to find a cell phone that works well 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. Roughly 60 percent of all cell phones sold in the US 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). To be sold in the United States as hearing aid compatible (HAC), a mobile phone or cordless handset must have a rating of at least M3 or T3.
In addition, many hearing aids (and cochlear implants) have a similar M and T rating to measure their sensitivity and their resistance to radio frequency interference. When shopping for a phone, to determine its compatibility with your hearing aid, simply add its M and T ratings together with those of the phone to create a combined rating. A sum of 6 or more makes a solid pairing. That hearing aid and mobile phone combination should work well for you. A sum of 5 is considered normal and should work fine for typical cell phone users. If the combined rating is 4, this is thought of as acceptable but not very usable if you make a lot of extended phone calls.
If you are shopping for a mobile phone online, you can usually use this combined rating to determine how compatible the phone you are interested in buying 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.