AES Vienna Video: NTI AL1 Acoustilyzer Speech Intelligibility Measuring Unit
How do designers and installers of public-address systems know if the system can be understood by the public being addressed? By being skilled and equipped in the science of speech intelligibility analysis. Acousticians measure speech intelligibility of speaker systems and the spaces they are installed in by feeding test signals (that cover the range of human speech and not much else) into the PA systems and reading/measuring those signals using specialized gear. One such device is the NTI AL1 Acoustilyzer analysis system, showcased here in this Gearwire video shot live from the floor of 122nd AES in Vienna, Austria. In this clip we get an introduction to the process and jargon of speech intelligibility analysis as we watch the NTI rep feed test signal through a small speaker, read it with the AL1 unit and represent the data in a variety of ways. Cool stuff.
NTI REPRESENTATIVE: I’m going to demonstrate for you how easy speech intelligibility measurement can be done with the Acoustilyzer and Mr. Talkbox. We just switch to this function, and just let’s go now -- let us go now to the Talkbox.
What we hear now is the STI-PA test signal which are modulated noise, noise pans, but the only thing we have to do is to play back the file and to play we press start on the Acoustilyzer.
[NTI REPRESENTATIVE DEMONSTRATING THE USE of THE NTI ACOUSTILYZER]
And I’ll mute the signal. What we see now, we have much ambient noise here but we have good speech intelligibility. We have a hearing scale from bad to excellent; the measurement we took now is good. We had an average speech level at the moment of 77 dB, A rated, and an STI value of 0.68. We can change it to the CIS value. It’s the common intelligibility scale. We store now all the results into the memory of the unit.
We can have a look at the detailed result of the measurement, showing us the bands of the measurement. So, we have octave bands from 120 Hz to 8 kHz. In each octave band, we have two modulators in there, and the algorithm basically looks at how good these modulations come to the unit.
Okay. Finally, I will show to you how the unit works together with the PC and we try now to get the measurements back from the unit to the computer. What we do now is to connect the Acoustilyzer to the USB port of the computer. We have started already the mini-link PC software but now what takes place is like a synchronization from the memory of the Acoustilyzer to the Pc. It’s like a digital camera.
You see now the two measurements we have done before: the sound pressure level we have stored and the steeper signal we have stored. We can make a double click on it, so we see now the detailed results. We have an STI value of 0.68 and they come into the intelligibility value of 0.83, all the detailed measurement results for your documentation.
Together with the mini-link PC software, you can also do online logging to the PC. So, if you, just for example, go to the RTA stream, we can stop and lock. Logging means that in this example, every 0.5 seconds, all the measurement values acquired by the Acoustilyzer are transferred to the computer and stored in SQ format on the PC. See now the values are running in here. I’ll first stop now to show you this is a complete look of everything you see on the RTA screen.
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