HP RM500SL manual FastFacts 17.3 DSL 5.0 in Speechmap

17.3 DSL 5.0 in Speechmap

The Desired Sensation Level (DSL) method is a systematic eardrum sound pressure level (SPLogram) approach to hearing instrument fitting that seeks to ensure amplified speech will be audible and comfortable while loud sounds will not be uncomfortable. It takes into account individual acoustic factors in audiometric and electroacoustic data. DSL was developed by the National Centre for Audiology (NCA), London, Ontario. Audioscan has implemented DSL within its Speechmap fitting system since 1994.

In 2005, DSL underwent an extensive revision. This has resulted in changes to speech targets for children. These changes will be more significant when the individual RECD values have not been measured for the child being fitted. See 17.4:DSL 5.0 changes and www.audioscan.com for details of the changes.

The Audioscan version of DSL 5.0 may differ from others in the following ways:

1)DSL 5.0 uses RECD values for ages > 119 months from a different source than for ages ≤ 119 months; Audioscan has used the RECD values for a 119 month old for ages > 119 months so all values come from the same study.

2)Input-output curve targets and compression threshold targets are not provided. Such steady-state parameters are of little value in estimating amplified speech levels. Matching amplified speech to the LTASS targets at levels from 50 to 75 dB SPL provides much better assurance that fitting goals are being met.

3)There is no provision to input the number of compression channels. This may be useful when the signal used for verification is not the signal for which the targets were developed. It is irrelevant when using real-speech signals to match speech targets and when using narrow-band signals to match narrow-band maximum output targets.

4)The term Uncomfortable Level (UCL) is used rather than Upper Limit of Comfort (ULC) in referring to the ear canal SPL that should never be exceeded.

5)Broadband output limiting targets are not provided.

FastFacts 17.3: DSL 5.0 in Speechmap

0611 RM500SL User’s Guide Version 2.8 Page 71