Question

How cotton wool absorbs sound waves?

Answer 1

It's actually simple concept.It may sound strange, but you can think of sound like a bouncy ball.

If the sound hits hard, flat surface,it will bounce off in predictableway with very small energy reduction.This is called sound reflecion.If the ball hits hard,but jagged or uneven surface,it will bounce off in a different random direction every time again with very little energy reduction.This ia called sound diffusion.

Now let's picture the ball hittinga soft cotton panel.The cotton absorbs a large portion of the ball's energy,so the reflection is minimal.

It maynot be the most scientific explanation,but it's a simple way to picture the absorption/diffusion/reflection properties of different materials.