RM500SL
®
User's Guide Version 3.4
June 2011
19 Speechmap Technical Details
Section overview
Speechmap provides a variety of stimuli for the testing of non-linear hearing aids with a
range of digital processing features. Additional information regarding the stimuli and their
analysis is provided in Appendix 2 of the printable User's Guide.
Speechmap stimuli
The Speechmap fitting environment provides a number of well-controlled, distinctly
different stimuli for both On-ear and Test box measurement modes. Four different digitized
speech passages (2 male, 1 female and 1 child) are provided as well as the International
Speech Test Signal (ISTS) and the single-talker International Collegium of Rehabilitative
Audiology (ICRA) distorted speech signal. In addition, one of the speech passages has been
filtered to provide 3 variations for evaluating frequency-lowering hearing aids. Pink noise at
levels of 50 to 75 dB SPL in 5 dB steps and a tone burst at 85 or 90 dB SPL are also
available.
The two “Speech-std” signals are by the same male talker, filtered to provide the long-term
average speech spectrum (LTASS) recommended by Cox & Moore (1988) for average vocal
effort. This is the LTASS assumed in the Desired Sensation Level (DSL) method of hearing
aid fitting. In addition, one of these passages (the Carrots passage) has been filtered to
suppress the 1/3 octave bands above 1 kHz by 30 dB with the exception of a 1/3 octave
band at 4 kHz (Speech4000), a band at 5kHz (Speech5000) and a band at 6.3 kHz
(Speech6300). These latter three signals may be used to determine the amount of
frequency shift provided by frequency-lowering hearing aids and the sensation level of the
lowered components of the speech signal. The ICRA noise, female and child speech signals
are presented as recorded with no spectral shaping.
The ISTS consists of 500 ms segments from recordings of 6 female talkers reading the same
passage in American English, Arabic, Chinese, French, German and Spanish. These
segments have been spliced together with appropriate pauses and filtered to match the
average female spectrum from Byrne et al, An international comparison of long-term
average speech spectra. J. Acoust. Soc. Am. 96 (1994), 2108-2120. The 15 second version
of this signal has been provided.
Live speech may also be used.
As a result of reanalysis of published data, the previous distinction between “soft” and
“average” vocal effort has been eliminated. Consequently, the speech, ISTS and ICRA
signals are presented unfiltered for levels from 50 to 70 dB SPL. At 75 dB SPL, the
spectrum is filtered to represent a “loud” vocal effort. An “own voice” filter is also available
at the 75 dB SPL level. This is intended to produce a spectrum and level at a BTE
microphone location similar to that produced by the voice of an average wearer.
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.
In test box mode, all signals are filtered to include BTE, ITE, ITC, CIC, 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.
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Summary of Contents for RM500SL
Page 1: ...RM500SL User s Guide Version 3 4 March 2010...
Page 9: ...RM500SL User s Guide Version 3 4 June 2011 EC Declaration of Conformity 9...
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Page 43: ...RM500SL User s Guide Version 3 4 June 2011 telecoil test 43...
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