How Does Sound Diffraction Affect What You Hear Through Barriers?

[Byrgg]

First, I'd like to mention that these are just some random questions I thought up about waves.

1. How can you hear sound through a barrier and why is it muffled when you hear it this way? I know waves are transmitted through materials, so I guess I'm really only asking why the sound is muffled when you hear it through a barrier.

2. Kind of part 2 of my first question, do waves diffract when they are transmitted through a barrier?

3. When waves travel, high frequency waves tend to be more directional because they have a high wavelength, and so they don't spread out much when passing through an aperture. This also explains why low wavelength waves are not as directional, they are not so straight-forward and linear when passing through an aperture any more. Is this right? And also, the waves are at the most circular when the wavelength of a wave is a bout he same size as an aperture. Is all that right?

My last topic sort of answered my last question, but I just want to confirm everything. Oh, and I think there was error, this might already accidentally be on another board here, but I meant to have this thread here.Thanks in advance.

 

[Byrgg]

Someone please reply.

 

[jtbell]

1. How can you hear sound through a barrier and why is it muffled when you hear it this way?

In general, part of the wave is reflected and part of it is transmitted and part of it is absorbed inside the barrier. This splits the energy of the original wave, therefore the transmitted wave has less energy than the original wave.

2. Kind of part 2 of my first question, do waves diffract when they are transmitted through a barrier?

If there are no apertures in the barrier, then it isn't appropriate to speak of diffraction which by definition has to do with the propagation of waves through apertures or around edges. In general, the wave is refracted as it goes through the barrier: it changes its direction as it enters and leaves the barrier. You can see this when you shine a narrow beam of light at an angle through a sheet of glass. The beam zigzags slightly as it goes through the glass, so the transmitted beam (in the air on the far side) is parallel to the incoming beam but shifted sidewise a bit. In principle you can get the same thing with sound waves, but it's difficult to generate a narrow beam of sound waves.

 

[Byrgg]

Ok thanks for the info.