Re: Singing pipes

[Leigh Palmer <palmer@sfu.ca>]

> 	Greetings everyone!  I saw an advertisement a while ago about a
> singing pipe.  You place a pipe that has a wire mesh inside of it over a
> bunsen burner.  When you remove the pipe from its heat source, it lets
> off a tone/moan.

These are called "Rijke tubes". The gauze is optimally placed one quarter
of the length from the bottom of the tube. The ones I've made are also of
50 mm diameter glass, with about 3 mm spaced brass wire gauze. I've made
quite a few of these and have kept a set which is tuned to a major triad
plus the octave. They are deafening!

I cannot explain simply (or otherwise) how these tubes work. Brian
Pippard (former Cavendish Professor of Physics at Cambridge) and I had a
go at trying to understand them during his visit to Simon Fraser thirty
years ago. After he left we continued a correspondence about them, and
he believed that he did understand them, but I was incapable of
understanding his explanation, which was nonmathematical. I saw quite a
bit of Brian during my stay in Cambridge a couple of years ago, but I
didn't renew the discussion. Brian told me that schoolboys in Britain
had made drainpipes sing by shoving lighted newspapers up into them from
below. I was unable to duplicate the feat, even with his help. He had
never done it himself.

What can be said confidently is that the tubes are powered by convection.
When mine are laid over sideways they become utterly silent. After being
left that way for ten seconds or so I can turn them vertical and they
sing loudly again, seemingly with no energy source. It is quite a
dramatic effect.

I, too, would like to know how these things work.

Leigh