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to generate less interference to hearing devices than phones that are not
labeled. M4 is the better/higher of the two ratings.
T-Ratings: Phones rated T3 or T4 meet FCC requirements and are likely
to generate less interference to hearing devices than phones 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 phone 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.
In the example to the left, if a hearing aid meets the M2 level
rating and the wireless phone meets the M3 level rating, the
sum of the two values equal M5. This should provide the
hearing aid user with “normal usage” while using their
hearing aid with the particular wireless phone. “Normal usage” in this
context is defined as a signal quality that’s acceptable for normal operation.
The M mark is intended to be synonymous with the U mark. The T mark
is intended to be synonymous with the UT mark. The M and T marks are
recommended by the Alliance for Telecommunications Industries Solutions
(ATIS). The U and UT marks are referenced in Section 20.19 of the FCC
Rules. The HAC rating and measurement procedure are described in the
American National Standards Institute (ANSI) C63.19 standard.
When you’re talking on a cell phone, it’s recommended that you turn the BT
(Bluetooth) or WLAN mode off for HAC.
For information about hearing aids and digital wireless phones
Wireless Phones and Hearing Aid Accessibility
http://www.accesswireless.org/Home.aspx
FCC Hearing Aid Compatibility and Volume Control
http://www.fcc.gov/cgb/consumerfacts/hac_wireless.html