[Andy.T]

Hi guys,

My son has homework, he has to build a soundproof box. Basically all the kids then take what they made at home into class and measure the sound of a metronome placed in the box from outside. I guess the quietest wins hehe.

I'm happy to make the box itself out of cardboard but what do you reckon would make a good insulator. Ideally I'd like to use household objects (jumpers, thick coats or something, maybe some spare carpet?) but I guess I could try the expanding foam stuff if you reckon that'd be loads better.

Any ideas would be great, the sooner the better as it's got to be in tomorrow hehe.

Cheers,

[dts_boy]

surely if youbuild it that would be cheating?! outragous behaviour, i would use that expanding foam stuff and then carpet as well!!! btw, seal the box watertight to reduce any leakage on cardboard edges

[Andy.T]

Obviously my son is the one building it I am merely handling the sharp objects and solvents hehe.

We've gone for about 4 layers of foam underlay so far and whilst that's good its not completely soundproof. I (or rather we) might try adding a layer of polystyrene.

[KraGorn]

I'd have thought polystyrene would be a good sound insulator, given its' large internal volume where sound will get trapped .. of course, my O-level Physics was 30+ years ago.

[shodan]

Make it perfectly square and airtight then nothing can be put inside to be measured, so a measurement of zero means... Winner!!!

Or is that just my thinking? No, I didn't do very well at school...

[Gary Lightfoot]

Airtight is good - if the air can't get out, then neither can sound. Use silicon rubber or decorators caulk which just happen to have lying around and seall all edges/joins etc. Polystyrene and carpet could work well, provided you seal all edges.

It might help a lot if you could make the box shut in such a way that it's as close to being airtight as posible - two layers of lids maybe for after you've put the metronome inside.

Gary.

[Andy.T]

Meant to reply earlier.

Thanks for all the suggestions, the box did ok in the end but wasn't the best. It ended up as a polystyrene box surrounded by rubber underlay within a cardboard box. The trouble was it wasn't terribly airtight due to the outer layer not being very rigid. It was, however, the best my son and I could come up with in the time (he thought it had to be in later in the week).

Anyway, thx again to all who gave pointers,