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Mobile phone
Some hearing aid users have reported a
buzzing sound in their hearing aid when
they are using cell phones, indicating that
the cell phone and hearing aid may not
be compatible.
The ANSI C63.19 standard determines
the prediction of compatibility between
a specic hearing aid and a mobile phone
by: adding the numerical value of the
rating for the hearing aid immunity to
the numerical value of the rating for the
cell phone emissions. A sum of 4 would
indicate that the combination of wireless
device and hearing aid is usable; a com-
bined rating that equals at least 5 would
provide normal use; a combined rating
of 6 or greater would indicate excellent
performance.
Whereas all hearing aids have acoustic
coupling, only the larger hearing aids
have the physical space for telecoil
(inductive) coupling. These two types
of coupling have different rating scales
(M1-M4 for acoustic coupling and T1-T4
for telecoil coupling, respectively) and
both ratings are therefore relevant
when predicting the compatibility of
a particular hearing aid.
For a hearing aid with both acoustic
coupling and telecoil coupling with a
rating of M4/T2 and with a telephone
rating of M3/T3), the combined rating
is 7 (M4 + M3) for the acoustic coupling
and 5 (T2 + T3) for the telecoil coupling.
According to the guideline given above,
both types of coupling will thereby be
acceptable, with the acoustic coupling
indicating excellent performance and the
telecoil coupling indicating normal use.