Audioscan Verifit - Manual (Page 91)

Verifit ® User's Guide Version 3.12  May 2015
18 Speechmap
Speechmap presents hearing threshold, UCL and amplified speech spectra as SPL in the ear canal. The fitting
goal is to make amplified speech audible and comfortable while avoiding discomfort for loud sounds.
Speechmap may be accessed from the Tests menu as either a Test box measure or an On-ear measure. See On-
ear or Test box mode for details.
Speechmap is normally used in SPL and this guide describes only this usage. See SPL or HL scale for details.
Speechmap facts
Speechmap is a trademarked hearing instrument fitting environment introduced by Audioscan in 1992. It
presents hearing threshold, UCL and amplified speech spectra as SPL in the ear canal. The fitting goal is to
make amplified speech audible and comfortable while avoiding discomfort for loud sounds. Originally speech
was simulated using amplitude-modulated tonal signals. The Verifit replaces these simulated speech signals with
real speech, both recorded and live. For details of the test signals and analysis methods, see Speechmap
Technical Details.
Speechmap departs from insertion gain target methods in presenting amplification goals in the context of the
residual auditory area, not as an isolated target line, and in the use of real speech, not tones or broad-band noise.
This is extremely important for non-linear hearing aids, analog or digital, because their processing is signal-
dependent. It also makes provision to correct audiometric data and 2cc coupler measurements for age-related or
individually-measured acoustic differences between real ears and the couplers used for calibration and testing.
The Speechmap environment provides two hearing instrument verification options: on-ear measures and test
box measures. See On-ear or Test box mode for details.
DSL 5.0 in Speechmap
Copyright DSL ® 2004. Version 5.0
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 resulting in DSL 5.0. It was further revised in 2007 to version
5.0a. See DSL 5.0 changes 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 up to and including
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.
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