The American Society for Testing and Materials (ASTM) utilizes the E84 combustion test to classify building materials used for interior construction according to their flame-resistance capabilities. This test measures the sound absorption coefficients at a specific frequency. For instance, ATS Acoustics 4 acoustic panels have an acoustic absorption coefficient of 0.68 to 100 Hz, and 1.10 to 250 Hz, which implies that the panels absorb approximately 68% of the sound they receive near 100 Hz (a bass note approximately 1.5 octaves below the average C) and, basically, 100% of the sound at 250 Hz (around the middle C). The first sample of foam, a ceramic-based acoustic material, does not burn and is classified as a Class A material.
The second sample, an acoustic polyurethane foam, will burn but eventually die out. It is a Class C material. The third foam, which is used as bedding and not as an acoustic product, ignites immediately and the flames continue to spread even after the source of the fire is removed. It is important to note that foam for bedding or packaging should never be used as an acoustic treatment on vertical surfaces such as walls or ceilings.