Sound waves(a neat experiment)

[Richard Brekne]

Ron Nossaman wrote:

> .....
>
> Note also that a ringing fork, twirled slowly next to your ear, gets quiet
> at 45° off plane.

Got to thinking a bit more about this that I suppose most of us have noticed
without thinking further about it. For the first I suppose this shows part of
why they call this kind of device a quadrapole. Any ways I decided to take your
test of putting the tuning fork on its side and listening to the sound when the
tines were vertically oriented and when they were horizontally oriented and go
a bit further with it by simply rolling the shaft 360 degrees around on the
table top. Sure enough the same affect. Louder and softer, exactly 4 times and
at intervals of 45 degrees. Doing the same with the butt end of the fork
yielded no difference in amplitude.

I see this as a very strong evidence that the side of the fork gets very much,
if not all,  vibration energy from the sides expanding and contracting, and not
because of what ever is happening along its length.

Note that this only speaks to the issue of how the fork works. I will know if
the panel propogates this wave structure by looking closer at where amlitidudes
are strong and where they are weak when the panel is excited by a fork useing
the sides of the fork.

>
>
> Interesting stuff about the forks we thought we knew.
>
> Ron N




--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html