Circle echoing phenomenon

[wiredspider]

I've searched all over and can't find an explanation for this weird effect. Our school has a little fountain area, it has some concrete structures around it for "art" and doubles for sitting. Now there are two areas that have semi-circles made of concrete and if you stand in center and say something, it "echos". I say "echos" because to me it feels more like a reverberation.

I'm going to link some pics that I took yesterday, but I know that other "echo circles" like this exist. Like here and I recall a long time ago seeing a similar circle type thing in the middle of the park on TV.

But I just don't know why, I think it does have something to with the way that sounds travel in concrete, anyone else know?

Pics here

 

[spidey07]

It's just the sound bouncing back and being focused at the center of the other parabola, so it is constantly repeated back and forth until all the energy in the sound wave is gone.

Similar to an ellipse which as two focal points.

 

[KillerCharlie]

Basic geometry they teach you in grade school FTW!

 

[spidey07]

Originally posted by: KillerCharlie
Basic geometry they teach you in grade school FTW!

Word, I thought they tought this in grade school?

 

[Tiamat]

The concrete structures act as a reflection point, and since they are all equidistant from you in the center, the magnitude of the reflection is quite large.

They still reflect otherwise, but there is constructive and destructive interference (both) when you are not in the center. When you are in the center, all of the reflection is of the constructive type.

 

[Fullmetal Chocobo]

OP, I had to check your location--we have the same thing happen here at Texas State University @ San Marcos near the library.

 

[wiredspider]

I uploaded some pics

And I think actually found the reasoning, concrete's absorption is very low, like the equivalent of a mirror according to wiki so in combination with the circle, it produces the weird effect. I don't think you get the same effect with just any kind of circle, ie crop circle .

 

[Tiamat]

Originally posted by: wiredspider
I uploaded some pics

And I think actually found the reasoning, concrete's absorption is very low, like the equivalent of a mirror according to wiki so in combination with the circle, it produces the weird effect. I don't think you get the same effect with just any kind of circle, ie crop circle .

Yeah, it has to be a reflective body, not absorptive. Put fiberglass over the concrete, and the effect would be minimized, perhaps eliminated.

 

[spidey07]

Originally posted by: wiredspider
I uploaded some pics

And I think actually found the reasoning, concrete's absorption is very low, like the equivalent of a mirror according to wiki so in combination with the circle, it produces the weird effect. I don't think you get the same effect with just any kind of circle, ie crop circle .

I would SO skate that place. It's a cornucopia of skateboarding goodness.