Speech – (RA)STI

Measuring STI/RASTI is a simple task with WinMLS.

The procedure is very fast and user friendly if you follow these instructions carefully. If you have any questions, please contact us.

If you have purchased a higher license version of WinMLS it is strongly recommended that you load the setup named Speech_All Parameters (STI RASTI ALcons etc.).

Click the help button for more information.

Click the Next button to continue.

If you have not loaded the settings for your sound card, go to Setup→Load… and select your sound card in the list shown in the picture.

Click the Load button to load the sound card settings. After doing this, you must reload this setup.

If you cannot find your sound card on the list, click help. The help file will give you instructions on how to set up your sound card.

Connect the loudspeaker or sound system to your sound card left output. If you do not want to connect to the sound card output, see the next wizard step on how to measure when the signal is not played back from the sound card.

Connect a microphone to your sound card left input.

Click help for information about testing the levels or go to Measurement→Test Levels.

Perform a measurement using Measurement→Start.

This setup is NOT configured to account for the background noise. Therefore if the background noise is less than 15 dB below the speech signal, the results will not be correct. Click help for more info.

Effects of distortion will not be considered either.

If you have a higher level WinMLS license, you can load a Speech-setup that consideres the influence of background noise and distortion.

If you want to measure other parameters than the speech parameters, load the setup named Room Acoustics_Reverberation Time.

The RASTI value is plotted as shown in the picture.

The default settings in this setup should give accurate results if the maximum reverb time of the room is < 2 seconds and if the harmonic distortion and background noise is not a problem as was discussed in the previous wizard step.

If you have purchased level 3 or higher you can calculate STI.If you have purchased level 4 or higher you can calculate ALcons.

To change to one of the above, go to Plot→Plot Type Settings→Active Plot (F5). In the dialog box, select the parameter you wish to display as shown in the picture.

In some cases it is more convenient to use an external source than to use the sound card output for playing the measurement signal.

For example if the source is placed very far away from the microphone or a sound system that does not have any direct input except a CD-player or can playback a .wav-file.

IMPORTANT: If you use WinMLS to record the signal, you must go to Measurement→System Delay… and select the setting in the picture.

Click help for more info.