Description of M and T Ratings:
When wireless devices are used near hearing devices (such as hearing aids and cochlear implants), users may detect a buzzing, humming, or whining noise. Some hearing devices are more immune than others to this interference, and wireless devices also vary in the amount of interference they generate.
The wireless telephone industry has developed ratings to assist hearing device users in finding wireless devices that may be compatible with their hearing devices. Not all wireless devices have been rated. Wireless devices that are rated will have the rating displayed on their box together with other relevant approval markings, such as on the website by the displayed phones.
The ratings are not guarantees. Results will vary depending on the user's hearing device and hearing loss. If your hearing device is vulnerable to interference you may not be able to use a rated wireless device successfully.
M-Ratings: Wireless devices rated M3 or M4 meet FCC requirements and are likely to generate less interference to hearing devices than wireless devices that are not labeled. M4 is the better/higher of the two ratings.
T-Ratings: Wireless devices rated T3 or T4 meet FCC requirements and are likely to be more usable with a hearing device's telecoil ("T Switch" or "Telephone Switch") than unrated wireless devices. T4 is the better/higher of the two ratings. (Note that not all hearing devices have telecoils in them).
Most phones that are rated T3 also have an M3 rating. Similarly, most phones rated T4 also have an M4 rating.
Hearing devices may also be measured for immunity to this type of interference. Your hearing device manufacturer or hearing health professional may help you find results for your hearing device. The more immune your hearing aid is, the less likely you are to experience interference noise from wireless devices.
Questions and Answers:
Q. When Hearing Aid Compatible handsets are tested for HAC compliance are they tested using the wi-fi functionality for certain models?
A. No. When HAC handsets are tested and rated they are done without the wi-fi functionality. HAC handsets are not rated with respect to wi-fi operations.
Q. Can I return the phone if it does not work for me after purchase?
A. Be sure to understand the return policy (listed here) and early termination fees before signing up for any cell phone or service. Since a cell phone's performance with your hearing aid can change depending on your location, your listening experience outside the store may be different.
Q. Do the FCC HAC regulations guarantee that I will be able to use a cell phone with my hearing aid?
A. While there is no guarantee, phones that comply with Hearing Aid Compatibility (HAC) regulations should improve usability for hearing aid users. Hearing loss and hearing aids are highly individualized so it is still advisable to try a cell phone with your hearing aid in the store before making your cell phone purchase.
Q. How do I know if my hearing aids will work with my cell phone?
A. Most new hearing aids contain RF immune circuitry and about half contain a telecoil. These digital hearing aids are designed to be usable with wireless devices with lower RF emissions and magnetic coupling ability. Your hearing healthcare professional will be able to tell you if your hearing aid is immune to RF interference and may need to contact the manufacturer of your hearing aid to determine its immunity rating. Your hearing healthcare professional will also be able to tell you if your hearing aid contains a telecoil.
Q. What if I cannot find a cell phone that works with my hearing aid?
A. You can check with your hearing healthcare professional to determine if there is a hearing aid option for you that may work better with cell phones. Some users may find that accessories such as neckloops may further assist with their use of HAC rated wireless devices and for using non-rated cell phones.