stereo export

[gas]

Koz

Just tried what you suggested. When I import the itunes version back into Audacity it is back into stereo again. So the problem seems to be with itunes, or something I am doing wrong with itunes. Either way, now that I know I have a stereo signal (at least on quicktime) I can put the track on an SD card and use it in the timing device.

gas

[kozikowski]

And, just when you thought it was safe to go back in the pool...

You know there's a trick to generating tone bursts, right? For some complicated math reasons, you can't just start a tone cold on the first cycle and stop it the same way. If you listen carefully, you can get a click on both ends. This can confuse equipment and if you compress or change the character of the sound, it can cause serious distortions.

I had to create a tone track for some testing. I used International A 440 Hz and I put a rhythm segment at the top, so you could tell on a loop when the show started over.

Boop, boop boop, booooooooooooooo...

On each beep, I faded in and out for three cycles. All the clicks and distortions went away.

Koz

[gas]

Interesting. We've actually used half a sine wave (positive) and so far the timing device seems to be recognizing it and doing what it's supposed to do (which is to wait 2 seconds for a response, and then shut off until the next sine wave. If we run into trouble at a later stage of development we will try your fade in and fade out idea.

gas

[kozikowski]

What's the tone frequency? This isn't audio any more. You are producing an arithmetic pulse not found in nature which may not survive going through many audio systems.

Produce about ten of these "tones" on a timeline and turn loose the Analyze tool with 8192 and Log Frequency. You would think you should get one peak at the frequency of the original sinewave, but I bet you get a whole family of harmonics and frequencies. The first time you send this thing through an audio system, you may find a buzzy click instead of the original pulse and the sensor may no longer work.

If you're using a very restricted in-house technology service, then it may not make the slightest difference. But if you start making this for other people, then it needs to conform to audio standards.

Here. Put 2 seconds of the "real" tone on a timeline and Analyze using 16384 (You may need to move this number a little). You should get one single spike at the tone frequency. Now cut the bottoms off of the first five or so cycles, cut and paste until the timeline reaches about a minute worth of these positive pulses.

Analyze that. When I do that, the analyzer window fills up. There is enough electrical trash and harmonics in there to kill.

Robust tone sensing is a lot harder than it looks. If you put straight pulses into a noisy environment, then you can get false triggering.

Koz

[gas]

Koz

Fortunatey I don't have to worry about all that. Your description of an "in-house technology service" is not far off the mark. What I'm working with is an intergrated timing device which sends a signal from one channel of the mp3 player to trigger the timer, while the person being evaluated listens to information being presented the other channel (hence the need to have two completely seperate channels). The person never hears the buzzy click, only the timing device receives that signal.

It's all part of developing what psychologists (of which I am one) commonly refer to as a "continuous performance test" that measures constructs such as attention, impulsivity, and reaction time. The vast majority of these tests are computer programs, and because we are talking about small differences of 10 to 50 milliseconds between subjects I've always been concerned that using these programs and comparing the results from differnt computer systems is probelmatic, not to mention the different sensitivties of hardware products like keyboards etc. Recent research has indeed shown that using these programs on differnt computer systems yields different results. Consequently, I decided to start working on an integrated "stand alone" system that bypasses all of the problems inherent in comparing results obtained from a myriad of computers.

gas

[kozikowski]

Not being willing to let sleeping dogs lie, did you notice that the tone sounds different after the MP3? Then if you remount the show in Audacity, it doesn't look the same, either?

You may have unintentionally walked into heavy audio technology. MPEG1 Layer 3 works by messing with the energy that lets you produce an "unnatural" audio signal. So you have two tasks fighting each other.


I'm crystal clear about what you're doing. My web site is full of test tools and signals I produced because I couldn't fix something using the current tools.

Koz

[gas]

So far so good. The device I'm using recognizes the signal and starts the timer as I had hoped. Now, if it ever gets to the point of "mass producing" the audio signals we may have a different story entirely. Just in case, what is your website address and can someone like myself utilize the test tools and signals you mentioned?

gas

[kozikowski]

It's kozco.com, but a lot of the more exotic stuff is hidden because they're dangerous. If you put a straight 20 to 20,000 audio sweep into a speaker, it will blow the tweeters into charred fragments.

I just hate it when that happens.

One of these days, I gotta straighten all that web site stuff out. I keep posting things up there for other people and then forgetting about it. It's like cleaning out the garage and the attic in the same day.

Next week for sure.

Koz

[gas]

I know what you mean.

Thanks for everything,

gas

[Pennywhistler]

I think this has to do with your import settings. Are you asking it to record two channels (or however many you are sending ito Audacity?

Also, there are various settings such as solo, mute, and split that you seem to be mucking up in some way (or have set incorrectly). WHEN IN DOUBT READ THE DIRECTIONS! It's all in there. I swear! I printed the whole thing out, which makes looking up things like this much easier than pulling up the PDF and spending 20 minutes searching for the correct settings..