What Causes the Pitch Changes in a Spinning Twirler Toy?

[hulkster]

Standing Wave/ Resonanace problem PLEASE HELP!

Ok. I've tried to answer this problem so many times now, but I just can't get it. Here it is:

A child's toy called a twirler, consists of a tube (like a hose, which is spun
in a circle above one's head. It is noted that at certain rates of rotation,
sounds of definite pitch are heard. What is the source of the sound? what are
the resonance effects? What is the relationship between pitch and rate of
rotation...?


Thank You in advance

 

[OlderDan]

Ok. I've tried to answer this problem so many times now, but I just can't get it. Here it is:

A child's toy called a twirler, consists of a tube (like a hose, which is spun
in a circle above one's head. It is noted that at certain rates of rotation,
sounds of definite pitch are heard. What is the source of the sound? what are
the resonance effects? What is the relationship between pitch and rate of
rotation...?


Thank You in advance

It will make a difference in the pitch if the tube is open on both ends or closed on the end being held. I assume it is open at both ends. You need to look at standing waves in a pipe, and think about two possible effects from twirling the tube. 1) Will the pressure in the tube change when it is being twirled? If it does, that will affect the speed of sound in the tube and that will affect the resonant frequency. 2) The doppler effect. The sound source will be moving relative to an observer hearing the sound from a tube someone else is twirling.

 

[DaveC426913]

The sound source will be moving relative to an observer hearing the sound from a tube someone else is twirling.

Woah. We're sorry, the English language has sustained a major back-injury and will be out for the duration the the game.

 

[OlderDan]

Woah. We're sorry, the English language has sustained a major back-injury and will be out for the duration the the game.

The sound source will be moving relative to an observer who is hearing the sound that is coming from a tube that someone else is twirling.

Can you understand it now? Did you really need those extra words?

 

[DaveC426913]

The sound source will be moving relative to an observer who is hearing the sound that is coming from a tube that someone else is twirling.

Can you understand it now? Did you really need those extra words?

No. Less.

"The sound source will be moving relative to an external observer."

 

[OlderDan]

No. Less.

"The sound source will be moving relative to an external observer."

External to what?? The tube?

This is ridiculous and you know it. I'm finished with the subject.

 

[DaveC426913]

External to what?? The tube?

This is ridiculous and you know it. I'm finished with the subject.

You're being deliberately obtuse, and you seem to be a bit defensive. I don't think that's really helping hulkster.

When I have more time I'll try to compose an answer.