From: SFPhysics@aol.com
Date: Thu May 08 2003 - 14:02:33 PDT
From: SFPhysics@aol.com Message-ID: <1df.88b55a2.2bec1fe9@aol.com> Date: Thu, 8 May 2003 17:02:33 EDT Subject: Vibrating Stick Speaker / Bone Phone
>In an Explo workshop last year, we attached the audio output of a radio (I
>think) to a small motor. Then
>we attached a stick to the motor. The stick vibrated. Bite on the vibrating
>stick and our mouths turned into speakers. I am using 1.5 V motors and I
>need advice on what to use for my audio output. The signal
>from my CD player is too weak to power the motor.
>Thanks, Jeff Friedman
>>
Back in the early 1970s when I first started doing the "Bone Phone" speaker
it was with quality ball bearing motors used for the solar cell
demonstrations. Cheaper motors with the three pole construction and weaker
magnets didn't work nearly as well. A good motor will work just fine with a
little transistor radio, CD player, cassette player, and the like. So, my
suggestion for you is to obtain a better motor. The 1.5 Volt motor you may
be using is most likely the wrong impedance to the audio signal and the
mismatch is causing a poor transfer of energy. The low current low voltage
ball-bearing motors are the way to go. These will work on as little as 0.25
Volts with high efficiency.
BTW - the Bone Phone idea came from Thomas Alva Edison, who was nearly deaf,
when he would bite onto a piano case side or phonograph cabinet to hear the
music. The year was 1878 when he first started doing things like this and
recorded these actions in his lab notebooks. After I did the Bone Phone in
classes at Lincoln High School, Gabe Espinza brought the Bone Phone to the
Exploratorium when he worked there in the 1980s as an Explainer. Glad to
hear Edison's "discovery" is still being used.
Another variation is to use a stiff stick (pencil) held in the teeth with a
plucked rubber band attached on the end to have the vibrations go through
your teeth and jaw into the inner ear. Neat effects... and it works best
when the loop of the rubber band is twisted into a single strand. Changing
the tension changes the pitch and students love discovering this. Many who
play guitar will understand the concept instantly.
Some dentists provide their patients with music on earphones just to keep
them from hearing the work being done on teeth through bone conduction. The
sound oftens scares the patient more than the actual work and music can mask
the dental work sounds.
Best wishes to all,
Al Sefl
Who has the perfect bone head for using a Bone Phone...
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