ABSTRACT
A highly audible interfering sound may be created in hearing aid outputs by the pulsatile
electromagnetic signals generated by some digital cellular telephones (DCT). At its
worst, this undesirable signal totally dominates the audio processing of the hearing
aid and makes it unusable. The degree of interference generated is a function of the
type of DCT technology, the type or style of hearing aid, and how many precautionary
measures have been taken in the hearing aid design to reduce interference. Engineers
from telephone companies and hearing aid engineers have worked together with the encouragement
of hearing aid consumers and the Federal Communications Commission to reduce this
interference problem. As a result, considerable strides have been made, particularly
by hearing aid companies, toward improving the immunity of hearing aids to DCT interference.
Many of these same engineers have participated in national and international standards
committees to develop viable methods for assessing the amount of immunity to DCT interference
provided by hearing aids and the emission levels from DCTs. The process of harmonizing
these standard assessment techniques is ongoing.
KEYWORDS
Interference - immunity - emission - digital - cellular - telephone
