Freeware (or usable demo/trial) acoustical measurement software? (other that SW!)

[mr_push_pull]

Hi everyone

Let's assume one can't get along with SW, reasons irrelevant.
Any serious alternative for MLS measurement? Free, usable demo/trial, of course.

[paologatto]

Sample Champion: http://purebits.com/

Many info are in the application notes section:
http://purebits.com/appnotes.html

The trial is fully usable for real measurements for 30 days.

Feel free to ask me technical questions about it or MLS method..

Bye,
Paolo

[mr_push_pull]

Originally posted by paologatto
Sample Champion: http://purebits.com/

Many info are in the application notes section:
http://purebits.com/appnotes.html

Thanks for the quick reply. I hope the demo doesn't have any limitation as upper frequency limit or the like.

Originally posted by paologatto
[B]Feel free to ask me technical questions about it or MLS method../B]

Be sure I will

[paologatto]

The demo has some limitations.. or what demo is?

But you can do almost all kinds of measurements..
Note that SC, differently from some other software, has a slow learning curve because has a lot of features and options (and requires some basic knowledge in what you are doing). On the other side this makes it very powerful and flexible.
So don't give up if you don't obtain perfect results after 5 minutes of use..

bye,
Paolo

[mr_push_pull]

All I need to do is measure the frequency response of drivers. With the aid of the app notes I hope the learning won't be so painful.

[ctviggen]

Hi Paolo,

Is there anything online that explains exactly how an MLS measurement works? For instance, once the impulse response is known, how is the frequency reponse determined? I used to be an electrical engineer and would like to know the mathemathics involved.

Thank you.

Bob

[mr_push_pull]

Originally posted by ctviggen
Hi Paolo,

Is there anything online that explains exactly how an MLS measurement works? For instance, once the impulse response is known, how is the frequency reponse determined? I used to be an electrical engineer and would like to know the mathemathics involved.

Thank you.

Bob

I second that question. Once I thought about writing a very basic MSL measurement SW (yes I'm serious), but never took the time to get into the theory involved.

[ctviggen]

Well, I think if you took an FFT of the impulse response, you'd get a frequency response. That makes sense. And that's why you want to select the portion of impulse response prior to the echo to get the response of the speaker and not the room. Hmmm...this software is a bit more powerful than ETF, which I have, as ETF is only for room response (i.e., you can't select a portion of the impulse response). I think that theory and reality are probably different, though -- for instance, do you just add all the frequency components from each window? That's probably what you do.

[paologatto]

Originally posted by ctviggen
Hi Paolo,

Is there anything online that explains exactly how an MLS measurement works? For instance, once the impulse response is known, how is the frequency reponse determined? I used to be an electrical engineer and would like to know the mathemathics involved.

Thank you.

Bob

On my website there are some very basic explanations: http://purebits.com/mlsteo.html

About the relation of the frequency response to impulse response (one is the FFT of the other for linear stationary systems), the theory is not strictly related to MLS but to linear systems.

For advanced info about MLS I suggest to read JAES papers from D.Rife, the first that applied practically MLS to audio measurements. He developed the MLSSA system.
Also papers by Schroeder, Vanderkooy, Vorlander and Mommertz are very interesting. Some Bibliography: http://purebits.com/bibliog.html

[ctviggen]

Thank you! Now, I just have to find those articles.