User's Manual

14
measurements of the near electric and magnetic fields generated
by wireless communication devices in the region controlled for use
by a hearing aid in accordance with ANSI-C63.19-2011 FCC has
granted a request for waiver of the HAC rules in section 20.19 for
dual band GSM handsets. The waiver has specific conditions, as
stated in the order (FCC 05-166) and expires 1 August 2007.
The purpose of this standard is to establish categories for hearing
aids and for WD (wireless communications devices) that can
indicate to health care practitioners and hearing aid users which
hearing aids are compatible with which WD, and to provide tests
that can be used to assess the electromagnetic characteristics of
hearing aids and WD and assign them to these categories. The
various parameters required, in order to demonstrate compatibility
and accessibility are measured. The design of the standard is such
that when a hearing aid and WD achieve one of the categories
specified, as measured by the methodology of this standard, the
indicated performance is realized.
In order to provide for the usability of a hearing aid with a WD,
several factors must be coordinated: a) Radio frequency (RF)
measurements of the near-field electric and magnetic fields
emitted by a WD to categorize these emissions for correlation with
the RF immunity of a hearing aid. b) Magnetic field measurements
of a WD emitted via the audio transducer associated with the T-coil
mode of the hearing aid, for assessment of hearing aid
performance. c) Measurements with the hearing aid and a
simulation of the categorized WD T-coil emissions to assess the
hearing aid RF immunity in the T-coil mode.
The WD radio frequency (RF) and audio band emissions are
measured.
Hence, the following are measurements made for the WD:
a) RF E-Field emissions
c) T-coil mode, magnetic signal strength in the audio band
d) T-coil mode, magnetic signal and noise articulation index