Finding displacement amplitude given frequency and pressure

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SUMMARY

The displacement amplitude of a sound wave with a frequency of 160.0 Hz in air at 20 °C, given a pressure amplitude of 29.0 Pa, can be calculated using the formula s = ΔP/(β*k). The correct value for β is 1.4 x 10^5 Pa, and the wave speed Vs is 343 m/s. The wave number k is derived from the relationship k = f/Vs, but it should be noted that k is also defined as 2π/λ. The correct displacement amplitude is 4.44 x 10^-4 m, although the initial calculation was deemed incorrect due to misunderstanding the relationship between k and λ.

PREREQUISITES
  • Understanding of sound wave properties, including frequency and pressure amplitude
  • Familiarity with wave equations and relationships, specifically ΔP(x,t) = (ΔP)cos(kx - wt)
  • Knowledge of the speed of sound in air at different temperatures
  • Basic grasp of wave number and wavelength relationships, specifically k = 2π/λ
NEXT STEPS
  • Study the derivation and application of the wave equation for sound waves
  • Learn about the relationship between frequency, wavelength, and wave speed in different media
  • Explore the concept of pressure amplitude in sound waves and its physical implications
  • Investigate the effects of temperature on the speed of sound in air
USEFUL FOR

Students studying acoustics, physics educators, and anyone involved in sound wave analysis or related engineering fields.

leinad0213
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Homework Statement



What is the displacement amplitude of a sound wave of frequency 160.0 Hz in air at 20 °C at the pain-threshold pressure amplitude of 29.0 Pa?

f = 160 Hz
Vs = 343 m/s
ΔP = 29 Pa

Homework Equations



ΔP(x,t) = (ΔP)cos(kx - wt) = β*s*k*cos(kx - wt)
k = f/Vs

The Attempt at a Solution



ΔP = βsk

Therefore, s = ΔP/(β*k) = (ΔP*Vs)/(f*β)

β = 1.4 * 10^5 Pa

So the answer I got was 4.44*10^-4 m which is wrong. Am I missing something here?
 
Physics news on Phys.org
k=f/Vs is not accurate, since k is 2π/λ

λf = Vs

ω/k = Vs
 

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