Is a resonant frequency any of the harmonics?

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SUMMARY

The discussion centers on calculating the length of a pipe with one open end and one fixed end to achieve a resonant frequency of 280.0 Hz, using the speed of sound at 343 m/s. The wavelength is calculated as 1.225 meters, leading to the first harmonic length of approximately 0.30 meters and the second harmonic length of approximately 0.92 meters. The participants debate whether higher harmonics, such as the third harmonic at approximately 1.5 meters, are valid for this configuration, with one contributor suggesting that the question implies a minimum length requirement.

PREREQUISITES
  • Understanding of wave equations, specifically V = fλ
  • Knowledge of harmonics in fixed and open-end systems
  • Familiarity with the concept of resonant frequencies
  • Basic principles of sound propagation in air
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  • Explore the principles of resonant frequencies in different pipe configurations
  • Learn about the mathematical derivation of harmonics in fixed and open-end systems
  • Investigate the effects of temperature and pressure on the speed of sound
  • Study the implications of harmonic series in musical acoustics
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Students and educators in physics, particularly those focusing on acoustics and wave phenomena, as well as musicians and sound engineers interested in the principles of sound resonance in pipes.

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1. The problem statement,λ all variables and given/known data
A drum skin is stretched over one end of a pipe, creating a resonant air column with one open end and one fixed end. How long must the pipe be to achieve a resonant frequency of 280.0 Hz? (Use 343 m/s for the speed of sound.)

Homework Equations


V = fλ

The Attempt at a Solution


My assumption is that a resonant air column means that any of the harmonics for a fixed and open end could be used in order to solve for pipe length.

1. Solve for wavelength:
V = fλ
343/280 = λ
1.225m = λ

2. Solve for "pipe length"
Knowing that the first harmonic is a 1/4 λ for a fixed and free end system, I divided 1.225 by 4 to get ~0.30m, which the book states is correct. But if that works for a resonant air column, the rest of the harmonics should as well. So I multiplied 1.225 by 3/4 to get ~0.92m. The book also states this is correct, but these are the only two lengths the book shows

However, could I not keep going to other harmonics to get greater and greater lengths? For example, the 3rd harmonic, I multiply 1.225 by 5/4 to get ~1.5m, which the book does not list. But is this not also correct?

Thanks for your help
 
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AAAA said:
1. The problem statement,λ all variables and given/known data
A drum skin is stretched over one end of a pipe, creating a resonant air column with one open end and one fixed end. How long must the pipe be to achieve a resonant frequency of 280.0 Hz? (Use 343 m/s for the speed of sound.)

Homework Equations


V = fλ

The Attempt at a Solution


My assumption is that a resonant air column means that any of the harmonics for a fixed and open end could be used in order to solve for pipe length.

1. Solve for wavelength:
V = fλ
343/280 = λ
1.225m = λ

2. Solve for "pipe length"
Knowing that the first harmonic is a 1/4 λ for a fixed and free end system, I divided 1.225 by 4 to get ~0.30m, which the book states is correct. But if that works for a resonant air column, the rest of the harmonics should as well. So I multiplied 1.225 by 3/4 to get ~0.92m. The book also states this is correct, but these are the only two lengths the book shows

However, could I not keep going to other harmonics to get greater and greater lengths? For example, the 3rd harmonic, I multiply 1.225 by 5/4 to get ~1.5m, which the book does not list. But is this not also correct?

Thanks for your help
I agree with you. Or you could read the question as "how long does the pipe need to be", suggesting a minimum length.
 
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Thanks for your help! :)
 

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