Hi Per, thanks for responding. I was unclear, sorry
That would give creeping waves (convex) not whispering gallery waves (concave) - WGW are Rayleigh's discovery way back when he noticed them in St Paul's in London. There's a nice animation here for the curious http://kino-ap.eng.hokudai.ac.jp/WG.html
But I was thinking of another type of thing - probably a special case of the WGW. When really young (5) I lived on the other side of Oz, and near me there was a small cave system that if you squeaked (I was young) the squeak would return a noticeable duration later. Presumably the sound made a round trip inside. So this isn't just a WGW, it was a WGW with no possibility of escape, only of being dampened by the amount of air it had to traverse. I thought the toroidal shape of a particle generating structure would be interesting - the amount of air would dampen any attempt at subtlety, but if the sound was loud enough, and the tunnel long enough, I thought it might naturally loop.
So I thought I would ask people if anyone had tried one.
Anyway, with people decommissioning such structures due to budget cuts around the world, perhaps someone conveniently located might get a chance to check one out if the occasion arises. If they were shutting it down, someone with a stack of amps and a suitable guitar+pedals might test the idea out.
(bootnote - I revisited the cave later and a rock fall had ruined the sound)
> Date: Tue, 28 Oct 2014 16:15:39 +0100
> Subject: Re: Acoustic looping
> From: firstname.lastname@example.org
> To: Loopers-Delight@loopers-delight.com
> I've done "acoustic looping" a couple of times but found that most
> natural, or architectural, ambiences tend cause too much diffusion for
> a really useful looping experience. The best set-up would be to play
> in front of a wall that is located in a flat environment with nothing
> else to cause diffusion to the echoed sound.
> Greetings from Sweden
> Per Boysen
> On Tue, Oct 28, 2014 at 11:53 AM, Ivodne Galatea <email@example.com> wrote:
> > Anyone here shouted or played a trumpet down the LHC at CERN (or a smaller
> > atom smasher). I imagine it would (if it worked at all) be like the
> > whispering galleries at St Paul's. If not, perhaps someone should (in the
> > interest of science, of course)
> > ig