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Mobile phone
Some hearing aid users have reported a
buzzing sound in their hearing aid when they
are using mobile phones, indicating that
the mobile 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 mobile
phone emissions. A sum of 4 would indicate
that the combination of wireless device and
hearing aid is usable; a combined rating
that equals 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 instruments have the
physical space for telecoil (inductive) coupling.
These two types of coupling have dierent
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
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