SP395 SoundPro Audio Integrator
Form7492
Operation Manual
62
7.
Column 500Hz Intensity Modulation
Rates
– Four Modulation signals of the 500Hz test
waveform used by RASTI to measure modulation reduction factor (m) and compute S/N
values.
8.
S/N Ratio Measurements
– values measured/computed by the RASTI test for each of the
modulation signals.
9.
Modulation Reduction Factor (m)
– values measured by the RASTI test for each of the
modulation signals
10.
Mean Value
– Mean value of the apparent S/N ratio values measured/computed within
the RASTI test.
RaSTI Function Operation
1.
Apply a test signal to the system.
Connect an amplified speaker to a CD player and
insert the RASTI test signal CD. The location of the speaker is the “speaker” location.
2.
Microphone -
Set up the SP395 microphone at the “listener” position. Use a stand, if
possible.
3.
Level
- Using the SPL meter function, set the level of the test signal as measured by the
SP395 to the “nominal” listening level. In most cases this will be 75-85dB SPL.
4.
RASTI -
Select the RASTI function on the SP395.
5.
Begin Test
Click on the ON/OFF field changing the “Off” to “Run”. This begins the test.
6.
Wait For test to complete -
Allow at least 12 seconds for the analysis to be completed.
7.
RASTI Result -
read the RASTI value on the bottom of the screen
.
Speech Intelligibility Results
Use this table as a guideline for evaluating the results of the %ALCONS and RaSTI tests.
%Alcons
RaSTI
Rating
57.70 0.20 Bad
44.00 0.25 Bad
33.56 0.30 Poor
25.59 0.35 Poor
19.52 0.40 Poor
14.89 0.45 Fair
11.35 0.50 Fair
6.60 0.60 Fair
5.04 0.65 Good
3.84 0.70 Good
2.93 0.75 Good
2.23 0.80
Excellent
1.70 0.85
Excellent
1.30 0.90
Excellent
0.99 0.95
Excellent
0.76 1.00
Excellent
