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Re: [Phys-L] Resonance with tuning forks vs small speakers



Maybe tuning forks are actually quite loud but hard to perceive because of
diffraction? Though the tines are relatively big and they have fairly large
amplitudes, the backsides of each tine make an expansion when the front
makes a compression and vice versa.

So, if we could get rid of the vibrations from the backside then, like in
the video of the small speaker, the sound would be louder.

I cut a rectangular hole in a piece of cardboard in the shape of a tine and
held it close but not touching the vibrating tine, and the volume went way
up!

Thank you for the help!
-Zeke K.

On Fri, Oct 28, 2022 at 12:42 PM Paul Nord <Paul.Nord@valpo.edu> wrote:

Zeke,

For starters, the tuning fork is really bad at radiating sound energy.
They make almost no noise at a distance. The tube acts much like the body
of a stringed instrument in helping the motion of the string couple to the
air. Phones, on the other hand, would need to work hard to design a
speaker that transmits anything to the air.

Take a look at the 39 minute mark of this video:
https://www.youtube.com/watch?v=ADgihdzVSRY

As for the human perception of "amplitude increase" it may be related to
the logarithmic nature of human hearing. Ten times more energy in the
sound wave doesn't sound 10 times louder.

Paul


On Fri, Oct 28, 2022 at 2:03 PM Zeke Kossover via Phys-l <
phys-l@mail.phys-l.org> wrote:

Howdy Physicists!

As a resonance activity, I bring a vibrating tuning fork towards a tube
that is open at one end and closed at the other. When tuned correctly,
the
air in the tube loudly resonates.

Since tuning forks are expensive and every student has a phone with a
speaker, I've tried running the activity with a frequency generated by
their phone. To my ears, the sound generated by their phones is way
louder
than the tuning fork, but when I put the phone next to the tube, the
amplitude increase is way less.

I wonder why they are so different. Do any of y'all have ideas?
--
*Marc "Zeke" Kossover | Educator, Teacher Institute*
zkossover@exploratorium.edu
Museum: Pier 15, San Francisco, CA 94111
Mailing: 17 Pier, Suite 100, San Francisco, CA 94111
_______________________________________________
Forum for Physics Educators
Phys-l@mail.phys-l.org
https://www.phys-l.org/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@mail.phys-l.org
https://www.phys-l.org/mailman/listinfo/phys-l



--
*Marc "Zeke" Kossover | Educator, Teacher Institute*
zkossover@exploratorium.edu
Museum: Pier 15, San Francisco, CA 94111
Mailing: 17 Pier, Suite 100, San Francisco, CA 94111

<https://www.exploratorium.edu/tinker>