In the past, the complex electronics of mobile phones often interacted poorly with the electronics of hearing aids, resulting in interference between the two devices that was perceived as static, screeching or whistling noises, or missing words. Fortunately, improvements in technology and new government regulations have made the question “Will this cell phone work with my hearing aid?” simpler to answer. To help consumers shop for the right hearing aid compatible mobile phone, the new regulations include a standard rating system and labeling requirement.

To understand how this rating system works, you should first understand the two modes that hearing aids work in – M mode (for microphone) and T mode (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. In T mode, the hearing aid instead uses an inductive process to pick up electromagnetic signals inside the phone directly, without the need for a microphone. The T mode is important when shopping for a phone, because at least 60% of hearing aids sold in the U.S. have one.

The two modes – M and T – are each rated on a scale of 1 to 4 where 1 is the lowest sensitivity and 4 is the highest. 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 themselves also carry M and T ratings to indicate their sensitivity and ability to block interference in each mode. To determine the compatibility between your hearing aid and a mobile phone you are considering, just add the M and T ratings together; add the M rating of the hearing aid to the M rating of the phone and add the T rating of the hearing aid to the T rating of the phone. A sum of 6 or more makes a solid pairing. That hearing aid and cell 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. 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.

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. In the end, nothing beats a real world test so you may want to wear your hearing aid to the mobile phone shop and test out a few different phone in real conditions.