Open-Ended Air Columns: Natural Freq of Cylinder?

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    Air Columns
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Discussion Overview

The discussion revolves around the natural frequency of an open-ended air column and its relationship to the hollowed cylinder that contains it. Participants explore whether the calculated natural frequency pertains to the air column itself or the cylinder, considering the implications of boundary conditions and the interaction between the air and the cylinder.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions whether the natural frequency calculated is for the air column or the hollowed cylinder, suggesting it may belong to the cylinder since the natural frequency of the air column should match that of the surrounding air.
  • Another participant argues that the frequency pertains to the container and the column as a system, emphasizing that both are necessary for standing waves to form.
  • A different viewpoint states that the natural frequency is indeed that of the air column, but notes that the cylinder has its own natural frequencies related to waves in its material, which can be excited if the cylinder is struck.
  • Participants acknowledge the complexity of the topic, indicating that initial learning often simplifies the system, which becomes more nuanced with advanced study.

Areas of Agreement / Disagreement

Participants express differing views on whether the natural frequency is attributed to the air column or the cylinder, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

Participants highlight that the surrounding air does not have a natural frequency in this context, as it supports traveling waves. The discussion also touches on the evolving understanding of the system as one progresses in the study of acoustics.

Who May Find This Useful

This discussion may be of interest to students and educators in physics and engineering, particularly those exploring acoustics, wave phenomena, and the interaction between different media in sound propagation.

Tam Le
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When we calculate the natural frequency of an open-ended air column, is the natural frequency we calculated pertaining to the air column or the hollowed cylinder containing the air column?

I imagine that the natural frequency belongs to the hollowed cylinder, for the natural frequency of the air column should be the same as the natural frequency of the surrounding air.
 
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The frequency is for the container and the column together as a system.
Without the container you don't have the refection you need for standing waves to form and without the air there is no medium for the waves.

Note: the surrounding air does not have a natural frequency in this context because it supports traveling waves by default.
 
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What Simon said.
It is the frequency of the air column, with the boundary conditions imposed by the cylinder.

However, the cylinder itself has natural frequencies that are related to waves propagating in the solid material of the walls. If you hit the cylinder, you may excite both air waves and the flexural waves in the cylinder.
 
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Thank you, Simon Bridge and nasu, for improving my understanding.
 
No worries.
When you start to learn this stuff you are only given the simplest pictures - as you advance you will be introduced to a more complete picture.
In the beginning the tube is treated as rigid and one dimensional for eg. Later you'll deal with other shapes.
 

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