Rational Acoustics



Arturo
March 4th, 2011, 12:14 AM
Hello everybody. I'm new to the board but have been searching and reading as much as I can. I got pretty comfortable with taking IR & TF measurements today in v7. It's amazing how quick one can capture and accumulate useable data. My question is how does one time a log swept sine file to play back in time to take an IR measurement? I created a 20Hz-20kHz log sweep aiff file 10.922 seconds in length to match the longest TC available. It plays back well. How do I time it to line up with the start of my IR measurement? Should I make the file slightly shorter than the TC? I've been lurking around this place for a couple of weeks and you guys are great. Thank you for all of the help that I have received without even asking a question.

Ferrit37
March 4th, 2011, 02:58 AM
hey Arturo,
you should be able to set the generator (alt+n) to play a file rather than pink noise.
haven't tried it myself yet though :)

adam
March 4th, 2011, 09:27 AM
Hello everybody. I'm new to the board but have been searching and reading as much as I can. I got pretty comfortable with taking IR & TF measurements today in v7. It's amazing how quick one can capture and accumulate useable data. My question is how does one time a log swept sine file to play back in time to take an IR measurement? I created a 20Hz-20kHz log sweep aiff file 10.922 seconds in length to match the longest TC available. It plays back well. How do I time it to line up with the start of my IR measurement? Should I make the file slightly shorter than the TC? I've been lurking around this place for a couple of weeks and you guys are great. Thank you for all of the help that I have received without even asking a question.

Arturo,

You could put a bit of dead space at the head and tail of your file. This will give you time to start and stop the measurement before/after the swept sine starts/ends.

It's not available yet but our swept sine generator does precisely this. The primary reason it's not available yet as we'd like to have a triggered measurement where the IR and noise start at the same time.

-A

Arturo
March 4th, 2011, 12:13 PM
Arturo,

You could put a bit of dead space at the head and tail of your file. This will give you time to start and stop the measurement before/after the swept sine starts/ends.

It's not available yet but our swept sine generator does precisely this. The primary reason it's not available yet as we'd like to have a triggered measurement where the IR and noise start at the same time.

-A

Thanks guys. I'm going to do just what Adam suggested and put a little space at the head and tail of the file.
Is the size of the TC integral to the length of the swept sine file?

Arturo
March 5th, 2011, 12:15 PM
Hey everyone,

I may have figured out a method of playing a swept sine file in Smaart and taking an IR measurement in time. I created a file with a 1k tone to cue me one second into the file then at three seconds the swept sine begins. The swept sine is 10.922 seconds long and if you time it right based on the 1k cue tone then you can get the entire swept sine to play within the 512k TC of the IR measurement. I've attached a copy of the file. It is a wav at 24bit 48k.

Let me know if this method works for anyone who wants to try it.

Daniel Ellis
March 21st, 2011, 12:52 AM
Do any of the Rational training classes cover this type of thing? I went to one of Harry's classes a couple of years ago and I learned a ton.. But I don't think we talked about using swept sine files.. But maybe we did and I just missed it because at the time I wouldn't have understood any of it anyways...

But anyways what kind of different information can you get taking your measurements this way rather than using pink noise? Is it anything that is worth doing while on tour tuning a rig in a room? Or is it more suited for use in the shop?

Arturo
March 21st, 2011, 05:25 PM
I can't really speak to the benefit of swept sine vs. pink noise for IR measurements because I'm still learning about this stuff myself.

If my understanding is correct, a swept sine impulse will provide better data about early reflections from a DUT in a room than pink noise will.

Someone please correct me if I'm wrong.

Ferrit37
March 22nd, 2011, 06:18 AM
hey Arturo,
I'm away travelling right now, but Prf Angelo Farina wrote a good paper on this and there's another by Swen Muller out there too.

FILO4PRES
March 24th, 2011, 07:32 AM
http://www.melaudia.net/zdoc/comparisonMesure.PDF

Here is the one by Swen muller. Its an excellent read!

Ferrit37
March 30th, 2011, 04:54 PM
Hey Guys,
Here's Angelo Farinas papers
http://pcfarina.eng.unipr.it/Public/Papers/list_pub.htm
:)

Arturo
March 30th, 2011, 08:49 PM
Thank you both!

I will get to reading those ASAP.