• hulkster
In summary, the sound source is moving relative to an external observer, and the resonance effects depend on the geometry of the toy.

#### hulkster

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...?

hulkster said:
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...?

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.

OlderDan said:
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.

DaveC426913 said:
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?

OlderDan said:
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."

DaveC426913 said:
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.

OlderDan said:
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.

## What is a standing wave?

A standing wave is a type of wave that occurs when two waves with the same frequency and amplitude travel in opposite directions and interfere with each other. This results in a pattern of nodes (points of no displacement) and antinodes (points of maximum displacement) that do not appear to move.

## How is a standing wave created?

A standing wave is created when a wave reflects off of a boundary and interferes with the original wave. The boundary can be a fixed point, such as a wall, or a boundary between two mediums with different properties, such as a string and air.

## What is resonance?

Resonance is a phenomenon that occurs when a system is driven at its natural frequency, causing it to vibrate with a larger amplitude. In the case of standing waves, resonance occurs when the frequency of the driving force matches the natural frequency of the system, resulting in a standing wave.

## How does resonance relate to the standing wave problem?

In the context of the standing wave problem, resonance occurs when the frequency of the driving force (such as a sound wave) matches the natural frequency of the system, causing the system to vibrate with a larger amplitude. This can lead to a standing wave pattern.

## What are the practical applications of standing waves and resonance?

Standing waves and resonance have many practical applications, such as in musical instruments, where standing waves are responsible for producing different notes. They are also used in technologies such as ultrasound imaging, microwave ovens, and radio communication. In addition, understanding standing waves and resonance is important in fields such as acoustics, optics, and electrical engineering.