How Do You Record Impulse Responses in Small Places?


I've only been able to experiment recording IR's in big reverberant places with balloon pops, I'm curious how you would go about recording some in places where a balloon can't be used like in a vacuum cleaner tube. I don't have access to use a starter pistol or studio monitors, so what other options are available that you guy's recommend I should try out?

Stephen Saldanha

Posted 2012-06-22T07:17:31.587

Reputation: 1 194



I have impulsed a number of ways. Balloon pops, belt snaps and tone sweeps through speakers. I like the speaker sweeps the best. Sound Forge comes with acoustic mirror and you can find the tone sweeps on their site. Acoustic mirror can deconvolve after you record the sweep. Voxengo deconvoler is another great one that you can even batch process. It can also generate the tone sweeps.

For small items I have used a car coax speaker or headphone. I suppose you could record a click and use that instead of tone sweeping. That would be that fastest way. Just make a square wave full scale for about 5 milliseconds and leave a second of space at the end. What I do is put a mic (typically omni to get the full range) in one end of a vacuum tube and the other a headphone\speaker. Record the tone sweep and then deconvolve. Since mics are small you can put the mic in whatever you want and have a regular speaker fire at it. Works fine.

BTW What I have heard with the balloon pops is a strange response because the air is imploding then exploding. The tone sweeps have a more true response.

Hope that helps. Drew

Drew Cady

Posted 2012-06-22T07:17:31.587

Reputation: 51

it takes loudness to really excite the space, doesn't it? what volume do you play those sweeps at? – georgi – 2012-06-23T21:57:14.407

Do even headphones turn out alright? – Stephen Saldanha – 2012-06-24T05:52:51.600


It doesn't explain much, but the Prometheus special features on talks a bit about the IP's made for the space helmets to make the ADR more fluent and easier. It shows a pic of the setup within the helmet (press pause). You'll see two mics at about 90 degrees and they used tone sweeps from a small speaker. The practice of creating IP's still completely baffles me...


Posted 2012-06-22T07:17:31.587

Reputation: 550