Quote:

Originally Posted by

**Sinusoidal** Gd Day,

I have absorbtion coefficients of a material available to me at thickness of 25mm , 50 mm and 100 mm respectively.

Is there a way to calculate the absorbtion co-efficient of the same material at 150mm using the data available ?

You may be able to extrapolate using the data. Approximately- the absorption will drop an octave for each doubling of thickness. Gas flow resistance will not be relative between thicknesses, however due to binding material, etc., so for a given material a smaller thickness would typically have a greater GFR.

According to the charts on

Bob Gold's page we see some confirmation:

Using OC at 3pcf or 48kg/m3 we see an absorption coefficient of .11 for 1" at 125Hz.

At 2" we have .17 so not quite.

At 4" it's .84 so not linear in the least at this frequency.

At 3" it's .53 and at 6" 1.19. There you go.

The

Porous Absorber Calculator will show similar trends.

Would you post it here for us to see how this works out compared to theory?