LG G6 User Manual page 164

Safety
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require digital wireless devices be compatible with hearing-aids. The intent
of the HAC Act is to ensure reasonable access to telecommunications
services for persons with hearing disabilities.
While some wireless devices are used near some hearing devices (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 noise, and devices also vary in the amount of interference they
generate.
The wireless telephone industry has developed a rating system for wireless
devices, to assist hearing device users to find devices that may be
compatible with their hearing devices. Not all devices have been rated.
Devices that are rated have the rating on their box or a label located on the
box.
The ratings are not guaranteed. Results will vary depending on the user's
hearing device and hearing loss. If your hearing device happens to be
vulnerable to interference, you may not be able to use a rated device
successfully. Trying out the device with your hearing device is the best way
to evaluate it for your personal needs.
M-Ratings: Devices rated M3 or M4 meet FCC requirements and are likely
to generate less interference to hearing devices than devices that are not
labeled. M4 is the better/higher of the two ratings.
T-Ratings: Devices rated T3 or T4 meet FCC requirements and are likely to
generate less interference to hearing devices than devices that are not
labeled. T4 is the better/ higher of the two ratings.
Hearing devices may also be rated. Your hearing device manufacturer or
hearing health professional may help you find this rating. Higher ratings
mean that the hearing device is relatively immune to interference noise. The
hearing aid and wireless device rating values are then added together.
A sum of 5 is considered acceptable for normal use. A sum of 6 is
considered for best use.