# Acoustic resonance

## Main Question or Discussion Point

Hey!

I understand frequency calculations in tubes, open ended or closed, however what would you classify a tube ring? Imagine a rube ring brushing against something constantly, if the tube was static and it made contact with something, you'll get waves travelling around in both directions inside the tube... now if if the tube was spinning whilst in contact with a surface, you'll have waves but there will be a phase shift in the 'backward' and 'forward' waves and get two resonant peaks.
My question is how do you calculate the frequency in this as it's basically an infinite length tube and do you even use the open/closed tube frequency formulae?

Thanks

## Answers and Replies

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I think I've mislead with the title...

There's a rotating inflated tube that is in constant contact with a surface. You can hear the noise from this contact and the frequencies have distinctive peaks due to the resonance in tube... I'm trying to figure out how to calculate mathematically those frequencies.