Bamboo As Sound Ammplifier?

[peter]

Hi; Physicists in this forum,

My son asked me a question that how a bamboo can amplify sound. He read on internet that putting a small (micro) speaker into a bamboo, the sound is louder, he thought that the louder of the sound is, the more energy is required, but putting the speaker into a bamboo does not input more energy, how does the sound become louder?

My question is that the sound is really louder in the bamboo?, if it is, how to explain it?

 

Thanks.

 

Peter

[Don Blazys]

The speaker vibrates and that creates sound waves.

 

Putting the speaker in the bamboo causes the bamboo

to vibrate along with the speaker and that creates

more sound waves.

 

In effect, the bamboo becomes a part of the speaker

so the speaker is, in that sense, made larger.

 

If your cell phone vibrates in your hand,

then it won't be very loud, and no one will hear it.

 

However, if it vibrates on a table top,

then it will be much louder, and everyone will hear it.

 

It's the same principle.

 

Don

[Turtle]

Hi; Physicists in this forum,

My son asked me a question that how a bamboo can amplify sound. He read on internet that putting a small (micro) speaker into a bamboo, the sound is louder, he thought that the louder of the sound is, the more energy is required, but putting the speaker into a bamboo does not input more energy, how does the sound become louder?

My question is that the sound is really louder in the bamboo?, if it is, how to explain it?

 

Thanks.

 

Peter

 

hi peter & son. :wave:

the sound is only louder in front of the opening of the bamboo tube. the tube focuses the sound energy that otherwise would be disbursed over a wider angle. the scientifc term for the tube is wave guide.

 

wave guide @wiki

...

Principle of operation

Waves in open space propagate in all directions, as spherical waves. In this way they lose their power proportionally to the square of the distance; that is, at a distance R from the source, the power is the source power divided by R2. The waveguide confines the wave to propagation in one dimension, so that (under ideal conditions) the wave loses no power while propagating.

 

Waves are confined inside the waveguide due to total reflection from the waveguide wall, so that the propagation inside the waveguide can be described approximately as a "zigzag" between the walls.

...

[peter]

Thanks a lot to all replies.

 

Peter