Thanks for the information.I bought one of these.
To be honest, it's well made, heavy and rather pointless. I wanted to record some stuff in the office studio that has external noises - notably a railway crossing with beeping warning and the trains. It's just a layer of perforated metal and foam, and made minimal difference. You can hear the effect is produces, but frankly maybe I expected more? Minimal impact down low, as you'd expect but some top end removal as outside noise goes through it. It works, after a fashion, but the thing is that singing or speaking into it is a bit oppressive and worse, it blocks vision, so a script or words doesn't work, and seeing the computer monitor is impossible too. Great idea for a project, but after the first use, it's back in the box.