audioscan verifit, User Manual

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Verifit
®
User's Guide Version 4.8 © November 2016
A tone burst (MPO) stimulus provides 128 ms bursts with 128 ms gaps at 1/3 octaves with a level of 90 dB SPL
in the test box and 85 dB SPL for on-ear mode.
A EUHA standardized MPO stimulus begins with 5 seconds of ISTS at 55 db SPL, followed by five tones at 90
db SPL (test box), separated by a 250 ms gap. The tones have a duration of 300 ms each, including a 25 ms
slope in and out, at 0.5, 1, 2, 3, 4 kHz. The total duration of the stimulus is 7.75 seconds (including the 250 ms
pause after the 4 kHz tone). The tones have a level of 85 dB SPL for on-ear mode.
In test box mode, all signals are filtered to include BTE, ITE, ITC, CIC, CIC-shallow, Body microphone
location effects. The selected overall rms level is established prior to filtering.
For fitting FM systems, the stimuli may be modified to represent the level (84 dB SPL) and spectrum at a chest
microphone location and the level (93 dB SPL) and spectrum at a boom microphone location. These are
presented in the test box in both on-ear and test box modes.
The overall SPL, 1/3rd octave band SPL, vocal effort and microphone location effects are given in the following
tables for the various broad-band signals available.
Stimulus spectra
Speech signals calibrated for matching to targets have the same LTASS as the ISTS. Modification for Loud
spectrum is from ANSI S3.5-1997. Modification for Own voice spectrum is from Cornelisse et al (1991)
adjusted to a 1 m reference.
The LTASS of the ISTS is the average female spectrum from Byrne et al (1994), which differs less than 2 dB
from the
universal LTASS (or International LTASS) suggested in this paper and less than 2 dB from the LTASS
of Cox & Moore (1988). For all practical purposes, they are equivalent.
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