Are there materials that are opaque to infra sonic waves? I have read that infra sonic sound waves because of their large wavelengths pass through most materials largely unabsorbed. However, are there materials that absorb infrasonic waves(could be frequency specific) very strongly? I have searched the web but have been unsuccessful in discovering an example. I asked this question writing "infrasonic waves" but if the absorption is very frequency specific(like, 'X' absorbs 20Hz very strongly) that answers my question too.
 A: Infrasonic waves propagate by physically moving the medium backwards and forwards with often quite significant amplitude. That is why you can feel amplified bass in music as well as hear it.
Anything spongy will absorb infrasound to some extent. My recipe would be rigid spaced panels with soft foam interior. However, the front and rear of the panel should not be rigidly connected.
A: One piece of news on spiral channel absorbers 

Acoustic absorption systems work by absorbing sound energy at a
  resonant frequency and dissipating it into heat. Traditional acoustic
  absorbers consist of specially perforated plates placed in front of
  hard objects to form air cavities; however, in order to operate at low
  frequencies, these systems must also be relatively thick in length,
  which makes them physically impractical for most applications. To
  remedy this, Assouar's group, whose previous work consisted of
  developing coiled channel systems, designed an acoustic absorber in
  which sound waves enter an internal coiled air channel through a
  perforated center hole. This forces the acoustic waves to travel
  through the channel, effectively increasing the total propagation
  length of the waves and leading to an effective low sound velocity and
  high acoustic refractive index. This allows them to make the absorber
  itself relatively thin, while still maintaining the absorptive
  properties of a much thicker chamber.

A: The question relates to materials so not sure if meta-materials would be a relevant answer. meta-materials 

were first suggested for electromagnetic waves in 1968 by Soviet physicist Victor Veselago.

However there was some work published describing how to apply the concept to protect against hearthquake waves. The link provides references to test with vibration at 50Hz and absorption higher than 80%.
Provided that this work is reproduced elsewere (I could not find links) it would stand to reason that this can be incrementally improved to a point where most the energy is absorbed or actually diverted away.
