Digital Cell Phones and Hearing Aids
- Part 1
Editor: The pending improved compatibility between hearing aids and
digital cell phones is great news for folks with hearing loss. But don't
get too excited! We're not yet where we need to be. Here's Linda
Kozma-Spytek with great information on this dynamic topic.
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Digital Cell Phones and Hearing Aids:
Frequently Asked Questions (and Answers)
Linda Kozma-Spytek, M.A., CCC-A, Research Audiologist
Copyright 2003 Gallaudet University RERC on Telecom Access
Q: WHAT CAUSES INTERFERENCE BETWEEN DIGITAL CELL PHONES AND HEARING
AIDS?
A: When using a digital cell phone, the telephone conversation is
transmitted over a wireless network using radio waves. The radio waves
emitted by the cell phone are referred to as radio-frequency (RF)
emissions. The RF emissions create an electromagnetic (EM) field around
the phone's antenna. This EM field has a pulsing pattern. It is this
pulsing energy that may potentially be picked up by the hearing aid's
microphone or telecoil circuitry and perceived by the hearing aid wearer
as a buzzing sound.
To complicate matters, the technology for transmitting calls over a
wireless network differs depending on the carrier or service provider.
For example, Verizon Wireless and Sprint PCS use CDMA technology, Nextel
uses iDEN technology, and AT&T Wireless, Cingular Wireless and
T-Mobile use GSM technology. The interference generated by these various
technologies has different characteristics, some of which may cause more
annoying interference for hearing aid users than others.
Telecoil users may experience another form of interference referred
to as "baseband, magnetic interference," which originates from
the cell phone's electronics (e.g., backlighting, display, keypad,
battery and circuit board). Unfortunately, baseband magnetic
interference occurs in addition to the RF-interference potentially
increasing the interference perceived by the hearing aid user.
The amount of interference experienced by hearing-aid users depends
on the degree of RF emissions produced by a particular digital cell
phone, and how immune his/her particular hearing aids are to these
emissions. This is also true for hearing-aid telecoil users, but in
addition, baseband emissions from the cell phone and the hearing aids'
immunity to baseband emissions must be considered.
Q: ARE DIGITAL CELL PHONES COMPATIBLE WITH HEARING AIDS YET?
A: Many hearing aid wearers still experience interference when using
digital cell phones, particularly if they use the telecoil for telephone
communication. Although there are no hard and fast rules, people with
in-the-ear (ITEs) or completely-in-the-canal (CICs) instruments
generally experience less interference than people with behind-the-ear (BTEs)
instruments, and newer, digital hearing aids are generally more immune
to interference than older, conventional analog hearing aids.
The Federal Communications Commission (FCC) recently (7/10/2003)
partially lifted the exemption to hearing aid compatibility (HAC)
requirements for digital wireless phones. The cell phone industry has
been given a phase-in period for compliance. For acoustic coupling to a
hearing aid's microphone, the new rules require each digital phone
manufacturer and carrier to have 2 commercially available handsets for
each transmission technology with reduced RF emissions within 2 years.
For inductive coupling to a hearing aid's telecoil, digital phone
manufacturers and carriers have been given an additional year (i.e., 3
years) to make available 2 handsets that provide telecoil-coupling
capability for each transmission technology they offer.
The new ruling also requires a standard method for measuring digital
cell phone emissions (i.e., ANSI C63.19) and product labeling on the
outside packaging of the phone. Volume control is not part of this new
requirement. However, most cell phones do have a volume control,
although there is a standardized upper limit on the sound level that
cell phones can produce. For more information on the new ruling, the
full report and order by the FCC can be viewed at http://ftp.fcc.gov/cgb/dro/hearing.html.
It's important to note that the FCC does not have regulatory
authority over hearing aids. This authority, although somewhat limited,
lies with the Food and Drug Administration (FDA). Even so, the FCC,
within its report and order, encouraged the hearing aid industry to test
and label their products according to the level of immunity they have to
digital cell phone emissions. The FCC and FDA are working cooperatively
on this issue, recognizing that compatibility requires the coordinated
function of both devices.
Part 2
