I examined the articles and videos about 'the tin can phone'. I concluded that all the articles and youtube videos about it are fake.
But now let's understand why the tin can phone articles are bullshit. Let's examine wikipedias article en.wikipedia.org/wiki/Tin_can_telephone Basically they begin their
article saying it works, without providing any technical prove. The whole article is anti-scientific bullshit.
They say: "When the string is pulled taut and someone speaks into one of the cans, its bottom acts as a diaphragm, converting the
sound waves into longitudinal mechanical vibrations which vary the tension of the string. " . In this quote, they deliberately and criminally omit what the
material the string is made of, nor they point out the shape of the "cans". The waves on the string are not longitudinal. They insolently lie that the sound from those cans can travel by a ... textile rope. They lie that it can travel if that textile rope is twisted. Absolutely idiotic. Horrifying! Also, the sound waves reflect off the solid
surfaces!
To confirm this, i read some articles and found the formula.
It is called Reflection coefficient. (there is also the transmission coefficient formula but I think it is not needed here).
You cannot simply transmit sound from air to metal because of impedance mismatch.
R=reflection coefficient and it is supposed to show how much sound reflects.
[formula image]
where p=density
c=speed of sound
z=impedance
since z=p*c, then
R=(z2-z1)/(z1+z2)
where z is impedance for longitudinal. z=density * speed
Zair=1.29 kg/m3 * 343 m/s = 442
Zsteel(the tin cans are made of steel)=7800 kg/m3 * 5790 m/s=45162000
Zwater=1000 kg/m3 * 1493 m/s=1493000
[airwater]
Reflection coefficient , water and air = 99.9% of sound is reflected.
[steelair]
Reflection coefficient, steel and air= 99.9% of sound is reflected.
There are 2 problems with this formula.
When water flows in my copper pipes, the metal pipes make noise, we hear it, which means that the sound from the metal is transmitted
into the air.
Maybe the sound simply travels on the surface of solid objects?
I did many tests. and conclusions are.
The string should not be coated in varnish nor in paint, should not be stranded and it should be made of metal. It should be clean and stretched very tight. The string should not
touch
anything even a light touch stops the transverse wave on it. An observation is that when the sound wave travels on (or in?) a very
thick metallic object such as
a big thick industrial nail, a pipe, etc. the sound does not stop when something touches the object. This means that if we want the
string to turn
, let's say a 90 degrees turn, we must connect it to a ticker piece of metal , lets say a thick metallic rod, nailed to a wooden
beam. And even in this case there might be losses.
The resonator box. Of course my first tests were with the tin can and did not work. What worked was this shape.
Only this shape [resonatorboximage] of the resonator box, made of juice box, converts
longitudinal waves in the air to transverse waves in the string , transmits them from air in the solid string.
I think, the walls of this resonator tremble probably because of the property of elasticity. The shape is similar to to the shape of the guitar.
The sound on the other end of the string , mine was 10 meters long, was of bad quality, with an echo.
The shape of the resonator chambers of the phonographs is horn, and men who own them should try this shape.
Actually the text above barely matters, because this radiator can transmit sound into metal! This is probably because of resonance
property. although it contradicts to the formula. Those 7.3 cm wide metal plates vibrate when I clap my hands. The sound travels in the pipes. [radiator]
Either way the article on the wikipedia should be corrected, and the one who wrote it should be banned, fired and disenfranchised.
A few comments about media. Video titled The WORLD's LONGEST TIN CAN PHONE! they kinda admitted their phone is non functional.