|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
|
|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
In Reply to: What does a NRC greater than 1 mean? posted by Scott H. Pultz on June 3, 2001 at 01:17:46:
[ When looking at acoustic foams, I often see NRC values that are greater than 1.0. If 1.0 means complete absorbsion at a given frequency, then what does a value > 1.0 mean? ]It means the test procedure chosen to test with is messed up.
Testing for NRC involves reverberant chambers, where the sound bounces around, and around, and around, much more so than normal room, and certainly in open spaces there are no significant reflections (except for the ground/floor).
A test sample can absorb some of the reverberant sound as it vbounces around the chamber, ans so absorb more of the totalmsound energy, since it is getting a shot on the second pass of the sound wave.
Do not look for flat NRC's, look for the lowest frequency of NRC, where the NRC has reached .7. This means more than absolute flatness, as much of the HF region can be "fixed" by a simple layer of polyester batting over the absorbing object.
As long as the NRC does not dip below 0.8 to 0.7 in the "passband", then do not worry about it.
Jon Risch
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: What does a NRC greater than 1 mean? - Jon Risch 06/6/0118:59:35 06/6/01 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
