Monday, April 3, 2017

Anechoic and Reverberation Chambers field trip

When I was little, my dad would sometimes take me over to the Science Building where he worked at BYU, and show me all the coolest things: the top of the pendulum, the giant ground sloth skeleton, the wave machine, and best of all the anechoic chamber. I LOVED going into this room where there were no echoes, no outside sounds—only the most silent, muffled air I'd ever experienced. And I would have given anything if, for this field trip, I could have just called up Dad and asked him to get out his key and go with us to the anechoic chamber again! But…now that he's gone…we had to go through the regular channels. And it wasn't too hard: you can just sign up for a tour here at the BYU Acoustics Outreach page. On the night we went, we were the only people in the group, so it was great.
The anechoic chamber has been remodeled since I was young: back then it was all made of yellow insulation, and the foam pieces weren't quite so aggressively triangular! So it was cool for me to see this updated version. Our tour guide was really knowledgeable and answered all the children's questions with great patience. (The little ones were kind of nervous about the wire mesh floor, and I remember feeling just the same when I was young! It feels very precarious. It's actually strong, though—they can put a grand piano on it with no problem!)

My only regret on this field trip was that I didn't get to walk around yelling and shouting with as much wild abandon as I felt like I could when I was there with my dad. :) And I wish I had thought to make a recording while we were in there! But, never fear: here is a recording made in another university's anechoic and reverberation chambers which will give you the idea.

Another bonus was that, unbeknownst to me, BYU now also has a reverberation chamber, which is basically the opposite of the anechoic chamber. And that was really cool too!
You can see all the hard angled surfaces they have hanging above the floor, all to increase reverberation.

The most amazing thing in this room was the demonstration our guide gave us of standing waves. He turned on a loudspeaker that put out a loud, low sound, and then we walked around the room listening. Because of the reverberation, the waves reflect back on themselves, and that means they sometimes make nodes, or places where the peaks and troughs of the waves actually cancel each other out. We had understood this in theory, but experiencing it in real life was really striking! You'd walk around, wanting to cover your ears because of the loudness of the sound, and then suddenly you'd come to a spot where the sound just…dampened. It became almost soft, as if you'd covered your ears or walked into a different room. And those places were the nodes. We loved this!

I didn't record that phenomenon, but here is a short sample of how a voice sounds in the reverberation chamber: 

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...