Sound proof box
I’m building an isolation booth for drums in my garage.
Drums are loud. In terms of decibels, John could probably play at 120dB easily. Comfortable speech levels outside are at about 70dB, so we need about 50dB of attenuation between the drums and the outside.
Here’s a plot of the attenuation we have, with no box, with the box itself, and with the box and the enclosing garage.
The box provides about 15dB of attenuation right now, though it is essentially transparent at 160Hz, 250Hz, and 500Hz. It’s 8 feet long, so that’s a round trip time of 16msec or so. We’d expect a resonance around 60Hz. Or this could be the self-resonance of the walls or window. Clearly we need some damping to improve this.
The garage doesn’t block anything below 100Hz, but it’s good for 10-15dB above that.
Need another 15 db overall to get to our target of 50dB of attenuation. I’m thinking a second layer of ply with some kind of damping or absorbtion will be necessary. Might be best to experiment with curtains or light duty acoustic tiles and then decide if we need the extra plywood.