What is CAM2 (previously called CAMEQ2-HF)?
CAM2 is a program that is used to determine initial
fittings for multi-channel compression hearing aids using the audiogram
alone. It is a software package that
runs under the Windows operating system on a PC. An extensive help file is included. CAM2 is a modified and extended version of Camfit. CAM2 gives gain recommendations for
frequencies up to 10 kHz, whereas Camfit only gives recommendations for
frequencies up to 6 kHz. The rationale
behind CAM2 and a summary of the differences between CAM2 and Camfit are described
in:
Moore, B.
C. J., Glasberg, B. R., and Stone, M. A. (2010). "Development of a
new method for deriving initial fittings for hearing aids with multi-channel
compression: CAMEQ2-HF," Int. J. Audiol. 49, 216-227.
Note that CAM2 is short for “CAMEQ2-HF”;
CAMEQ was one of the two fitting rationales implemented in the Camfit
software. “HF” stands for “high
frequency”.
The hearing aid can have any number of
channels up to 22. The program determines the gains and compression ratios that
should be applied in each channel, or at the standard audiometric frequencies,
based on air-conduction audiometric thresholds. If an air-bone gap is present (i.e. if the loss has a conductive
component), both air-conduction and bone-conduction thresholds should be
entered.
To use the program it is necessary to
specify the characteristics of the hearing aid, specifically, the number of
compression channels, the edge frequencies of each channel and the compression
threshold of each channel. Some example aids are pre-defined, and there is an
option to enter and save the specification of any other aid. The program is
used separately for each ear, but the recommendations are intended to give good
results when the client is fitted bilaterally.
The output of the software includes the
following:
(1) Insertion gains for
speech or a speech-shaped noise for levels from 50 to 85 dB SPL (assuming a
speech spectrum that does not vary with level)
(2) Real-ear aided gains for
speech or a speech-shaped noise for levels from 50 to 85 dB SPL
(3) Compression ratios for
speech or a speech-shaped noise
(4) Insertion gains for
sinewave signals at the channel centre frequencies
(5) Real-ear-aided
gains for sinewave signals at the channel centre frequencies
(6) Compression ratios for
sinewaves at the centre frequency of each channel
(7) Insertion gains for
sinewave signals at the audiometric frequencies
(8) Real-ear-aided gains for
sinewave signals at the audiometric frequencies
Outputs (1) – (3) are independent of the
characteristics of the hearing aid, while outputs (4) – (8) do depend on the
characteristics of the hearing aid (e.g. the widths of the channels).
The software takes into account whether or
not the client has previous experience with hearing aids. Gains are slightly reduced for clients with no previous
experience.
Buying CAM2
CAM2 is sold in two forms. For individual
hearing aid dispensers, it is available as a stand-alone Windows program for £180
(UK) or $300 (US). This fee is for is a single-practice license; the purchaser
agrees not to pass the program to any other user. Purchasers should send a
cheque for £180 or a check for $300 to:
PROF. BRIAN C.J. MOORE
DEPARTMENT OF EXPERIMENTAL PSYCHOLOGY
UNIVERSITY OF CAMBRIDGE,
DOWNING STREET, CAMBRIDGE CB2 3EB
ENGLAND
The cheque or check should be made payable
to B.C.J. Moore. Credit cards cannot be accepted.
For manufacturers wishing to incorporate
CAM2 within their own fitting software, source code can be made available. Interested
manufacturers should contact:
bcjm@cam.ac.uk