Surface absorption

[manowire]

New user here. What are the numbers in the room simulator meant to reference? I have read ‘average absorption 200 hz and below” and have also read ‘per cent of surface covered with absorbing material”. I am dealing with plaster walls behind which have several inches of denim insulation with fairly high absorption ratings. Not sure how to depict this in the room simulator. Thanks in advance for any help/guidance.

 

[srossi]

In terms of acoustic room absorption the denim insulation has no affect. Use absorption coefficients of a plastered wall appox. .02-.05.
The denim backing does affect sound transmission from one side of a wall to the other.

 

[DanDan]

Que? Of course the denim insulation has significant absorption, which will remove energy from the room tone/decay. But as well as depth of absorption, area is also extremely significant.
Several inches is however not much in terms of Alpha (Absorption Coefficient) at LF. So wildly guessing 4" might have an averaged Alpha below 200Hz of say 0.4
Then measure your surface area of the room, plus surface area of absorption to get the percentage that REW is looking for.

 

[manowire]

Thanks very much for the guidance.

 

[srossi]

QUE?

Could you please explain the wall construction in more detail. If the denim material is not directly exposed to the room sound field it will have little contribution to the room absorption.

"I am dealing with plaster walls behind which have several inches of denim insulation..."

In the extreme case - if the wall was steel putting absorption material behind the steel would not change the surface absorption of the steel.

 

[manowire]

Basement. Concrete block walls for 2 of 4 walls. All four walls are Wood framed. 3.5” ultra touch denim insulation 16” on center on all four walls. All four walls are plastered & painted. Ceiling is thin vinyl 24” square tile with 5.5” ultra touch denim insulation between floor joists above. Hope this helps with relevant details requested.

 

[srossi]

Reflective wall materials	125 Hz	250 Hz	500 Hz	1 kHz	2 kHz	4 kHz

Plasterboard (12mm (1/2″) paneling on studs)	0.29	0.1	0.06	0.05	0.04	0.04
Plaster (gypsum or lime, on masonry)	0.01	0.02	0.02	0.03	0.04	0.05
Plaster (gypsum or lime, on wood lath)	0.14	0.1	0.06	0.05	0.04	0.04

 

[DanDan]

I'm a bit confused, is the Ultratouch in or on the walls. Vinyl tiles are probably quite reflective. I would replace those with fully absorbent such as Armstrong Optima.

 

[manowire]

Thank you. In the walls and ceiling under plaster on walls & 24” thin vinyl tile on ceiling. Carpet on floor.