T60 Reverberation Time Testing Question

[Rob45]

I am going to do a measurement on a larger space than I've tested before - where I've gotten by with a hand-clap - and I'm wondering if there are guidelines for the excitation sound level required? When can I use a large balloon (a friend uses a 36" dia. balloon), for example, and when would I need a gunshot or more? Obviously, balloons are easier to transport via air than pistols, but I have a range of firearms from the noisy to the horrendously noisy - e.g, 165+dB at 1 meter.
Is there a guideline based on the room volume and room constant?
Specifically, I'll be testing a space 25' x 29' x 19' high that initially is highly reverberant (T60 predicted 10.6 sec.), but then it will be treated to a predicted T60 time of 1.2 sec.
Thoughts?

Thanks,
R

 

[GregLocock]

I can't see an issue with using 165 dB source if your mic can handle it, but like you up til now all I've ever used were balloons or claps. I did qualify the Lotus VSAC using a B&K sound source and steady state measurements over the floor, but we didn't work back to reverb times. The Gaydon VSAC was large enough to include a driveby simulation, but that was my first NVH job and I can't remember how we checked the frequency response of the room, it may be my boss had already done it as part of the commissioning as he was pretty good at that sort of thing.

Cheers

Greg Locock


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[Rob45]

Greg, Thanks. The more I think about this, the less likely I think there'll be a problem: I think I'll just try the balloons first, then if necessary, a pistol using just a shotgun primer, no powder. If the mike were to overload, I'd just move the pistol farther from the measuring location.
It'll be fine.
If anyone's interested, I'll post a brief summary of how it turns out. We're using 2" Eckel panels for absorption, btw.
Thanks again,
R