INTERACTION OF A MONOCHROMATIC PLANE WAVE WITH AN IMPEDANT MATERIAL

Animations

 Version française

  

acoustics animation page

You can use images and animations included in this page for teaching using, but please acknowledge where you obtained the animation!
here : Catherine Potel (Université du Maine - France) and Philippe Gatignol (Université de Technologie de Compiègne - France)

See the slides associated to chapter 4 of the fluid acoustic course  


NORMAL INCIDENCE



The (complex) reflection coefficient for acoustic pressure amplitude is given by:
, where is the admittance of the material.
The (complex) acoustic pressure can be written as

which makes appear a standing part and a propagative part. The more the material is close to a rigid wall, the more the reflection coefficient is close to the value 1, and the more the standing part becomes preponderant.
The cartographies below represent the amplitude of the real part of the acoustic pressure,
with a color level (red = maximum, blue = minimum)
Material having a very high impedance (beta  close to 0)
champ incident
Incident field propagating
in the direction y<0		 champ réfléchi
Reflected field propagating
in the direction y>0
champ total
Whole field having a very great stationary part and a weak propagative part
Material having a very weak impedance (beta  very great)
champ incident
Incident field propagating
in the direction y<0		 champ réfléchi
Reflected field propagating
in the direction y>0
champ total
Whole field having a stationary part and a great propagative part




OBLIQUE INCIDENCE
carto champ incident oblique
Incident field propagating in the direction y<0		 carto champ réfléchi oblique
Incident field propagating in the direction y>0



carto champ total oblique
The whole field has a stationary character along y, but has a propagative character along x