I can't seem to find the data I want on acoustic absorption characteristics for Rockwell. Assuming the same density, are the absorption properties of Rockwell and Fiberglass, equal? If not, what are the equivalent densities? If there is a table or chart to show the comparison, that would be appreciated.
Thanks in advance for any info.

I don't have a table in front of me, but they are pretty darn close, so either will work fine. Just keep in mind that when using mineral wool you will need to have a frame as it is not as rigid as the 703 or 705.

Glenn

Thank you Glenn.
I thought they were pretty much the same, as long as the density was equal, but a friend thought he had read something that suggested otherwise.

No sure what your friend was reading but yes they are very close.

Those materials (as well as acoustic cotton like Ultratouch) have specs that are more or less interchangeable, meaning that they are closer than the accuracy/tolerance of the measuring process itself.

Generally I like using whatever material is least expensive, though there are some benefits to each material (for instance, 705 holds its shape the best, cotton is green-friendly, etc).

Agreed. If you use something like mineral wool you will need to build a frame.