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 earlier 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.
CAM2 is sold in two forms. For individual hearing aid dispensers, it is available as a stand-alone Windows program; the purchaser agrees not to pass the program to any other user.
For manufacturers wishing to incorporate CAM2 within their own fitting software, source code can be made available.
CAM2 is marketed via Cambridge Enterprise, which is part of the University of Cambridge.
For further information please contact: