15 Cochlear Update | FM Solutions
FUNCTIONAL LISTENING EVALUATION
Confirm that the FM system is operating properly by listening with
earphones through the receiver while someone is speaking into the
transmitter (or the transmitter is plugged into an audio source). Perform
a functional listening evaluation in the classroom both with and without
the FM system. Choose a listening task in which the listener can score in
the range of 50 – 80% correct. Administer it speech-only, in quiet, using
the processor alone at normal sensitivity. The child and examiner should
be 3 feet (1 metre) apart. The suggested presentation level is 60 dB SPL,
measured at the listener’s ear. Repeat testing in quiet through the FM
system only by setting the mixing ratio to ‘Telecoil only’ when using a
neckloop receiver, and to ‘Accessory only’ if using an ear-level or body-
worn receiver (via the CR110 Remote Assistant). Performance in these two
conditions should be similar. If not, the FM receiver settings may need to
be optimised.
Prior to completing the remainder of the functional listening evaluation,
the functional operating range of the FM system should be measured.
FUNCTIONAL OPERATING RANGE
To measure the operating range, turn away from the listener and continue
to talk into the transmitter microphone while walking away. Instruct the
listener to indicate when the signal becomes noisy or starts to break up.
If the signal is not clear at a separation distance of 12 to 15 feet (4 to 5
metres), try a different FM channel. Make note of the distance that is
reached before the signal deteriorates. Compare the performance at this
separated distance to the performance at 3 feet (1 metre).
Repeat the listening task at a distance of 12 to 15 feet (4 to 5 metres) in
front of the listener, adding in background noise (e.g. recorded multi-
talker babble) played at approximately 65dB about 3 feet (1 metre) in front
of the listener. Performance in noise should be similar to performance in
quiet at the same distance.
Note: Some manufacturers provide a list of recommended FM channels.
The use of these channels will ensure an optimum operating range.
7. Functional testing
considerations
Prior to fitting
a fm system
listening
evaluation in
the classroom
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