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One Man's Quest To Find The 'Sonic Wonders Of The World'

Wednesday, February 19, 2014

Ever wonder why your voice sounds so much better when you sing in the shower? It has to do with an acoustic "blur" called reverberation. From classical to pop music, reverberation "makes music sound nicer," acoustic engineer Trevor Cox tells Fresh Air's Terry Gross. It helps blend the sound, "but you don't want too much," he warns.

Cox is the author of The Sound Book: The Science of the Sonic Wonders of the World. He has developed new ways of improving the sound in theaters and recording studios. He's also studied what he describes as the sonic wonders of the world — like whispering arches and singing sand dunes. His sonic travels have taken him many places, including the North Sea, where he recorded the sound of bottlenose dolphins underwater, and down into a revolting Victorian era sewer, where he discovered a curving sound effect he'd not heard before.

Interview Highlights

On how a gunshot in an anechoic chamber — a room that absorbs the reflection of the sound — is quieter than a snap

You walk into this chamber through some very large steel doors and the first thing that kind of strikes you is you're [standing] on a trampoline floor of wire, because all around you on the floor, on the walls, and on the ceiling are these strange gray foam wedges, and they're there to completely absorb any reflection. So when you hear the gunshot all you hear is the shot coming straight from the gun, or in this case, the microphone and there's no effect of a room at all. ... We don't normally hear sounds without the effect of a room. We normally have walls around us reflecting sound.

On whispering galleries

There's a variety of them around the world. In England the most famous one is St. Paul's Cathedral in London, where you go up to the base of the dome ... and you whisper into the wall and the sound skims around the inside of the dome to be heard by your friend who is way, way across on the other side. It sounds like the sound is emerging from the walls and you can have a conversation 100 feet apart from each other.

On how to design a concert hall

We want this reverberance — this sense [that] the sound lingers a bit after the orchestra finishes for a couple of seconds. [It] is typically a design criteria. And to do that, concert halls are really very large. So normally, if you sit in a concert hall and look up you'll see it's a huge volume, really high ceiling, that's to give you that reverberance.

But also we want to get rid of things which deaden the sound, you know, soft stuff like curtaining and carpets are all bad news. If you look around a concert hall, all the walls and the ceiling are really hard materials. There's a sort of myth around the concert halls made of wood that wood vibrates but if you were to take the wood off you'd find it's glued to concrete behind. There's no way that wood is vibrating at all.

And a third, key criteria is to make sure we get lots of sound from the sides. If you ever hear one of those concerts when they play outdoors, it sounds a bit remote, like the people are playing on the stage from a distance. In a concert hall, you're kind of surrounded by sound, that sense of envelopment is created by sound coming from the side.

On how sound travels underwater

[Sound travels] more efficiently [in water] than in air. It's the same kind of process in the fact that you've got a wave, and air is being passed from air molecule to air molecule, whereas in water it's being passed from water molecule to water molecule. It just happens to be that in water it goes further, which is another reason why aquatic animals like to use it — because it can travel huge, great distances underwater in a way that it never would do in the air. It would die away much quicker.

On why thunder "rumbles"

What's amazing about thunder is when you hear it, it's actually got that crack and then it's got the rumble afterwards. As a kid, when you drew thunderstorms you would've drawn the lightning with that jagged line. If you didn't have that jagged line, you wouldn't have the rumble of the thunder.

... The visual look of lightning is really crucial to how the thunder sounds. ... Each little kink is actually generating the sound, and ... the sound takes different time to come from different kinks because they're all slightly different distances from you. That's the reason you get that very distinct rumble sound.

Copyright 2018 Fresh Air. To see more, visit Fresh Air.

View this story on npr.org

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