Sound in a vacuum

[rosaliemb]

Can anyone recomend equipment for demonstrating sound in a vacuum? Please.
ie What's the best setup, where can I obtain a reliable/safe pump , what have you used sucessfully? etc

Thanks, Rosalie (another one)

[RosalieM]

We use the bell jar and bell jar pump from serrata. You can do all sorts of demonstrations using it including bursting a balloon. Do a search for bell jar I think and you will probably come up with some other good ideas. I am pretty sure it has been discussed already - have fun!

[smiley]

I bought a great unit from scientrific. To vary the experiment, we put a kids iPod in the jar, and sucked the air out until we couldn't hear it. Because The apparatus has a tap on it, and a gauge, we were able to let the air in slowly and determine when we could hear it again.

[noona]

Like smiley we got ours from scientrific and use a small radio in it and it works very well

[Whspa]

I've got the Scientrific Vacuum jar as well. It will evacuate to -90kpa, but the bell (suspended) is still audible. And my balloon only partially expands - nowhere near bursting. How do you get a better result?

[sunray18]

Whspa - me tooooooo.. the sound is still there even though faint.
The sound of the pump is too loud as well.
we used to use an old bell jar set up so bought a new one a few years ago from Serrata - no better.
WHAT is the secret?

[smiley]

Guys, place it on foam rubber or a thick blanket. Otherwise your whole benchtop becomes a sounding board.

[Loopy]

I remember someone said here that they don't try to listen for the bell when the pump is on, but listens to hear the bell when they can after the pump is turned off. Rather what Smiley said in her post. I thought it's a rather clever twist on the experiment!

[superbug]

we use shaving foam or hair mousse.