AFMG Network Forum

Langston Holland · Member

I finally found a design limitation within SysTune that is significant enough to delay my plans to purchase the Aubion X.8 interface.

I need the ability to play much longer files as a custom signal type. The manual's excuse of "memory limitations" is about 10 years out of date.

After attending the Syn-Aud-Con intelligibility seminar last weekend with Bruce and Charlie, I put together a sound system test file that is just under 3 minutes long and includes everything I need to measure at a given location in a room. It's made up of short introductions, the STIPA v4 stimulus for a period of time long enough to comfortably store (3) direct measurements, (2) contiguous 512k log swept sines that I'll capture about mid-way through the 2nd sweep in SysTune, and finally silence for noise floor measurement. I'm sure I'll make adjustments to this with time, but I need to be able to do this kind of thing.

At present I'm using CLIO's ASIO based audio interface as the audio hardware for SysTune and it works quite nicely, but forces me to use both CLIO and SysTune to perform measurements. This requires me to take a helper to move the mic and record STI values with the handheld device while I operate the computer. This is really dumb considering how nice SysTune's NGINX Webserver is.

If I could have SysTune make use of some of the huge amounts of RAM available in modern computers (say 5 minutes at 48k/16bit max), I could buy the X.8 interface and do the measurements far more simply and economically.

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After experimenting a bit, I'm again able to answer my own question - though I still want the ability added to loop long stimuli of my design. Please. :)

The solution I found was to open (2) instances of SysTune, place them both in web serving mode, load the STIPA stimulus as a custom file in the 1st instance and the internally generated 512k log sweep in the 2nd instance. Google Chrome on my iPad 3 addressed both in separate browser tabs and worked nicely. I simply play the STIPA stimulus when needed or the log sweep when needed.

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Langston Holland · Member

Sad news - the 512k FFT length limitation in SysTune renders the STIPA v4 stimulus unusable. The ISO standard calls for a minimum 20 second period using this stimulus in direct measurements, but I'd hoped that the loop of the shorter segment length imposed by SysTune would work since it sounds to the ear like it repeats every second or so. Obviously this is not the case.

Looping the 512k beginning of the original 100 second long stimulus produced the same distorted STI reading whether played back through SysTune or Audition v3. Audition's playback of the full 100 second stimulus provided by Embedded Acoustics resulted in identical scores as using an iOS device for playback as intended for their product (I use iSTI Pro).

So I'm back to needing an extended stimulus playback time from SysTune in order to use it's web interface for multiple stimuli playback capability.

Bruce · Member

Bruce · Member

Langston Holland · Member

Good points Bruce and thanks for the link to that ASIO media player - I had no idea something so clean and simple like that existed for ASIO.

On CLIO's ASIO based audio device, it's output is pretty much unusable unless you use CLIO to generate or play back the signal. Only then do you have control over output level which can be as high as +16dBu. When playback is done with another ASIO application such as SysTune or Audition, the maximum output level is about -27dBu and I have no idea why.

So you're right about the X.8. It's getting more interesting given that its designed to work perfectly as a stand alone interface as well as having gain compensation within SysTune. :)

Sander got an email from me today on the 512k STIPA v4 stimulus request. It sure sounds repetitive when listening to it, but I tried various things with Audition to trim his 100 second stimulus down to 512k without success. Measured STI values decreased by about .4 no matter what I tried (not .04, but 0.4!). There's something fancier going on there than meets the ear.

Tomorrow I'm going to make a couple of dozen 65dBA measurements in a large church with SysTune's internal 512k log sweep and iSTI Pro on an iOS device. I'm looking forward to using the room's noise floor measurements in SysTune to see if that brings the indirect sine sweep STI values close to Sander's amazing work.

I made a bunch of STI measurements in my home this weekend and got consistently high values, so I'm going to have to take a different approach in convincing my wife that I can't understand her...

Bruce · Member

Sander has replied to me and pointed out that the 100 seconds was a minimum based on the common multiplier of the modulation frequencies, so at this point it looks like a dead end.