Measuring the impulse response
From DRC
Measuring your room response is easy. At it's most basic get a pencil, paper, SPL meter and a CD which plays some test tones at you. Sit around for a couple of hours and plot it out.
Much faster and more effective is to use a computer based FFT analyser. Several free and commercial systems are available to do this, you can get a simple one from this site which will run on windows, linux or Mac!
- Simple Automated IR Measuring Tool
- ETF: http://www.etfacoustic.com/
- Sample Champion: http://www.purebits.com/
- Aurora plugins: http://www.ramsete.com/aurora
- MLSSA: http://www.mlssa.com/
- CLIO: http://www.audiomatica.it/
- Audua Speaker Workshop: http://www.speakerworkshop.com/
- The MLS system provided with the Nwfiir Audio Tools suite
- LAUD resume writing services
- TEF
The theory behind the log sine sweep method is explained in this paper: link
All of these play sweeps or chirps into the room and measure what actually happens using an accurate microphone. Curiously enough accurate microphones are not hard to come by and are available for very little money. I use a Behringer ECM8000 which costs around £35 GPB.
Also rather interesting is that you DON'T need a very accurate PC sound card. Most of these systems use a loop-back connector from the soundcard output back into the input in order to calibrate themselves. So to a large extent you can get away with a cheap and nasty soundcard resume as the measuring tool (there are some exceptions to do with Windows kmixer mangling the sound before it even gets to the soundcard)
Under windows you may want to look at Jones Rush's guide which is available here: DRC_Guide_v1.0.pdf However, it's a bit of a faff to follow and I will shortly make available some windows/linux software which can make an all in one push button measurement of your impulse response.
...need more details...
