Why concave reflectors work better than a plane reflector

[SFB]

Hi


I have read several papers and found that for both sound beam /light beam , the sound pressure obtained is higher when a concave /curved reflector is used in place of a flat reflector. Can anyone tell me why?

Is it related to soem consideration of energy loss from the wave? If possible , please also provide soem resources so that I can better understand the phenomenon.



Thanks

 

[K^2]

Because you are within a space between 0F and 2F, where F is the focal length of the surface. If you are outside of that distance, you'll find intensity to be lower.

Draw yourself some parallel rays hitting a concave surface. They all meet at point 1F away from the surface (focal length). The density of the lines is going to be higher than in the initial beam between 0F and 2F.

 

[SFB]

Thanks !it really helped . It would be great if you can help me with another confusion. I have seen that in case of acoustc levitation (levitating partcle to nodes by creating a stading wave where sound pressure can overpower gravity), people have mostly used a spund source and a reflector on the opposite end leaving both sides exposed to air.

What difference would it make if I introduce side walls between the reflector and source rather than keeping it exposed to air. How would transmission loss relate to the boundary condition on the sides?