question regarding furnace filters and drywall-Acoustics Forum-Acoustic Fields Forum

Hi everyone!

Furnace Filters:
A few months ago I was at a voice actor’s apartment. He had placed a few furnace filters around his space to serve as diffusion. They were spaced from the wall about 2 inches. The filters were I believe, 18 x 24 inches in dimension.
He believed these work well, but I did not say anything, although I do not believe he verified this scientifically. So my question is, do these furnace filters really offer any measurable diffusion? I don’t think they do but I could be wrong.

Drywall:
Most homes are built with drywall, but most professional studios are constructed of quality hardwoods on the floor, walls, and ceiling.
In the SOWA project video, reference is made to replacement of drywall with hardwood. Awhile back I sent a sample read from our home studio to an audio engineer. He mentioned it sounded like drywall construction due to: (Something I didn’t understand when he said it… :) ). In other words, I did not understand what he was referring to, but it sounded like the drywall was contributing *Something* to the noise characteristics of the space.
So my question here is, what undesirable acoustic artifacts are introduced by drywall construction?

Thanks!

Jason