Reflection, Refraction and Diffraction

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Reflection, Refraction and Diffraction
Introduction to Acoustics

• University of Salford
• Acoustics Audio and Video Group

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Learning Outcomes

• Define reflection, refraction and diffraction
• Explain how refraction and diffraction occur
• Calculate angles of reflection and refraction

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Reflection and transmission

• There is always some reflected and some
  transmitted sound
• the impedance seen by the wave at the boundary
  controls the amount of reflected sound

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Absorption

• From we find
• Incident
• Reflected

• Reflection coefficient
• Absorption coefficient

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Refraction c2ltc1
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Refraction c2gtc1
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Refraction equation

• Snells law
• Two cases
• c2ltc1 always refraction
• c2gtc1 refraction only for small ?i

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Refraction in the atmosphere
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Diffraction
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Conclusions

• At a boundary, sound is both reflected and
  transmitted - controlled by impedance
• Transmitted sound may be refracted - controlled
  by sound speeds in the two regions
• Sound meeting an object may be diffracted -
  controlled by size relative to wavelength