Audioscan Verifit 2 - Manual (Page 79)

Verifit ® User's Guide Version 4.2 © June 2015
foam tip, they will be based on average earmold tubing.
For Test box Speechmap involving BTE instruments the earmold tubing must be considered. If the BTE is
coupled to the 0.4cc coupler using the personal earmold, the tubing effects will be part of the measurement. If
the TRIC adapter with HA-4 tubing (earmold substitute) is used, the 0.4cc wideband coupler WRECD will be
converted to an HA-4 0.4cc WRECD. As with the threshold correction above, the use of the earmold in RECD
will include the effects specific to the client’s earmold, otherwise an average earmold is assumed.
The following describes acceptable RECD measurement protocols and Test-box Speechmap coupling
combinations for BTE instruments and the implications of each in the test box simulation.
ANSI S3.46 method:
WRECD On-ear measurement: Audioscan WRECD transducer + foam eartip
Test-box Speechmap coupling: client’s personal earmold + 0.4cc wideband coupler
With this method, WRECD is a property of the ear only, and not dependent on the transducer or sound
source coupling. The earmold effects will be part of the measurement in the test box. Measured WRECD is
appropriate for coupler simulation and error is minimized.
Alternate method #1:
RECD On-ear measurement: Audioscan WRECD transducer + client’s personal earmold
Test-box Speechmap coupling: HA-4 tubing (earmold substitute), TRIC adapter, and 0.4cc coupler
This method utilizes the client’s personal earmold for the on-ear RECD measurement. The 0.4cc WRECD is
converted to HA-4 reference with earmold effects retained and is applied in Testbox Speechmap.The error
introduced is the difference between the earmold effects when connected to the hearing instrument receiver
and earmold effects when connected to the WRECD transducer.
If the total earmold tubing length is less than 35mm, it is recommended that Foam tip be selected in the
WRECD Coupling field. This will bypass the correction and increase accuracy for small earmolds.
Alternate method #2:
RECD On-ear measurement: Audioscan WRECD transducer + foam eartip
Test-box Speechmap coupling: HA-4 tubing (earmold substitute), TRIC adapter, and 0.4cc coupler.
Since the RECD here is measured with a foam eartip, an average earmold is added to obtain an HA-4
RECD with earmold effects. The error involved will be the difference between the actual earmold and the
average used.
Alternate method #3:
RECD On-ear measurement: Audioscan WRECD transducer + client’s personal earmold
Test-box Speechmap coupling: client’s personal earmold + 0.4cc wideband coupler.
An average earmold will be subtracted from the measured RECD to obtain a 0.4cc coupler WRECD without
earmold effects. The actual earmold will be introduced during test box simulation, but error will exist equal
to the difference between the earmold measured on the RECD transducer and the average earmold that was
subtracted.
79