Acoustic Foam vs Semi rigid fibreglass

I often read in forums (Gearslutz etc) ongoing arguments about polyurethane bass traps (such as ours) versus semi rigid fibreglass. It is often stated that polyurethane will not absorb low frequencies, which is absolutely false. Thin wall panels won’t absorb low frequencies but a large volume corner trap is very effective in absorbing low frequencies. The data below makes for interesting reading. This comparison was performed a few years ago at the Riverbank acoustic laboratory in the US. It compares a large Auralex trap (polyurethane foam) with a semi-rigid fibreglass trap of the same volume, and a flat fibreglass corner design. The polyurethane foam edges out the fibreglass in a close run race! Both are suitable for acoustic control.