Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: mriver8 on 25/10/2014 21:07:32

Title: What gives foam it's sound absorption properties?
Post by: mriver8 on 25/10/2014 21:07:32
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Title: Re: What gives foam it's sound absorption properties?
Post by: evan_au on 27/10/2014 10:06:57
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 (http://www.engr.uky.edu/vac/ME610/Lectures/Chapter%207%20Sound%20Absorption%20and%20Sound%20Absorbers.pdf).
Title: Re: What gives foam it's sound absorption properties?
Post by: phist1e on 28/06/2018 11:18:59
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. :/
Title: Re: What gives foam it's sound absorption properties?
Post by: yor_on on 29/06/2018 23:54:31
Cool  phist1e

More of that
Title: Re: What gives foam it's sound absorption properties?
Post by: Bored chemist on 30/06/2018 16:39:28
In general, sound is strongly reflected by  hard dense surfaces. Foam is neither.