[Lineshape]

On Apr 21, 12:23*am, Louis Boyd wrote:
RichD wrote:
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich

It should be simple *to demonstrate a Galilean telescope (one positive
and *one negative lens) *which will magnify or minify an acoustic image
* using an ultrasonic imaging *device and some *common optical lenses.
They would only *need to be made of a material with a different velocity
of propagation of sound *than a liquid they are submerged in. *The
velocity of propagation of sound is somewhat *analogous to the velocity
of propagation of electromagnetic energy to demonstrate refraction at
material boundaries.

"Magnify" doesn't have the same meaning in imaging and *non-imaging
situations.

An acoustic "telescope" doesn't have to be refractive. *A two mirror
Cassegrain reflecting telescope *can *focus sound as well as
electromagnetic energy. * I've experienced that working on microwave
antennas.

I remember a demo using a balloon filled with CO2 to focus sound,
though spheres as lenses aren't exactly great for building a
telescope.... Pretty neat way to show a sound analog to optics and
get the ideas of propagation velocity across to intro physics
students.

Not sure I'd like to use a balloon as a hearing aid though...

Frank.