[mriver8 (OP)]

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[evan_au]

Sound absorption works by turning sound energy into heat. Sound absorbent foam often has an an open pore structure - the narrow, winding channels, and changes in area of the pores produces many opportunities for sound waves to interact with the walls, creating turbulent flow and turning the sound into heat.

A somewhat technical description here.

[phist1e]

It's acoustic foam that has sound absorbent qualities, it's designed to improve room acoustics, rather than soundproof. Many people are under the impression that this is a soundproofing foam, but as you correctly stated it absorbs wave energy. Depending on the quality of the foam, the more wave energy is absorbed and this is determined through an NRC rating which ranges from 0 - 1. The NRC rating gives an indication of the percentage of energy that is absorbed by the foam. For example, if a piece of foam received an NRC rating of 0.60 it would absorb up to 60% energy. There are some good diagrams of how works in a room set up to improve acoustics, but I'm not allowed to post the external link. Sorry. :/

[yor_on]

Cool  phist1e

More of that

[Bored chemist]

In general, sound is strongly reflected by  hard dense surfaces. Foam is neither.