Sound absorption coefficients, with a source on every row

How to read this table

Each number is the Sabine absorption coefficient in that band: how much energy the material keeps, between 0 and 1. A 0.90 at 500 Hz means it sends back barely 10% of what reaches it at that frequency. Values above 1 show up in real tests because of diffraction at the edges of the sample; they are not typos.

The mounting matters as much as the material. The same panel flat against the wall and spaced 100 mm off it are two different curves, which is why they appear as two rows. Confusing them is the most common way an acoustic calculation ends up promising something the finished room does not deliver.

NRC is the average of the 250, 500, 1000 and 2000 Hz bands rounded to 0.05. It is useful for comparing at a glance and useless for designing: it is computed without looking at 125 Hz, which is exactly where almost every problem in a small room lives.

Where the data comes from

From manufacturer data sheets and published acoustic literature. Each row says which of the two and, when the manufacturer declares it, the test standard. If you find a figure that does not match the manufacturer's current sheet, write to acustega@gmail.com with the link: it gets corrected and credited.