ceiling

Ptownkid · Post by **Ptownkid** » Fri Sep 03, 2004 10:47 am

Which of these would be better for keeping sound out of the basement?

knightfly · Post by **knightfly** » Fri Sep 03, 2004 4:19 pm

If that "3" rigid" refers to rigid fiberglass insulation, the answer is neither - in order to do a decent job of isolation, you need two centers of mass, separated by as large an air gap (filled with insulation) as you can get. For mid and higher frequencies, using reilient channel or isolating clips and hat channel on the bottom of the joists and hanging two layers of 5/8" gypsum wallboard works well.

There is a lot more info on these questions already posted here -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=2125

The top two links on that page have the most info on sound proof construction... Steve

Ptownkid · Post by **Ptownkid** » Sat Sep 04, 2004 6:43 am

Ok, i'm kinda confused now.

I'm NOT using drywall at all, the ceiling is rigid covered in cloth. Does that mean that putting insulation above that is useless, and if not, where should it be?

giles117 · Post by **giles117** » Wed Sep 08, 2004 3:20 am

What it means is that you will get absorption of internal audio but no isolation from external audio based on your design.

You only have 1 leaf showing. The existing floor.

knightfly · Post by **knightfly** » Wed Sep 08, 2004 3:51 am

Insulation above your rigid fiberglass would help absorption of sounds inside the room, but do virtually NOTHING for isolation between your room and the rest of the world - check out my concept drawing near the bottom of the first page of this thread for the correct placement of different types of material to see what works for isolation -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=2033

Keep in mind that things that make the room sound better inside have almost nothing to do with what keeps the sound either in or out... Steve

Ptownkid · Post by **Ptownkid** » Wed Sep 08, 2004 9:08 am

Ok, so how much of an effect will using the safe and sound have between the joists? Let's say we're talking about internal acoustics here. Should I bother using it at all?

knightfly · Post by **knightfly** » Wed Sep 08, 2004 10:07 am

If you don't need isolation, filling behind the rigid fiberglass will increase the absorption somewhat - if cost is a factor, I'd forget it. If not, you might see another 10% absorption down to the point where your total depth= 1/4 wavelength of 90 degree incident sound, and a bit lower for grazing incidence (non-perpendicular) -

Did that make any sense? Steve

Ptownkid · Post by **Ptownkid** » Wed Sep 08, 2004 10:14 am

Sorta, but in laymens how does that affect the sound in the room? I'm assuming that the amount of absorbtion that one would require is based on personal taste.

knightfly · Post by **knightfly** » Wed Sep 08, 2004 11:33 am

Actually, what you want in a control room is a fairly short reverb time so you can hear what your recordings are doing - a more live room, and any simulated room done in a digital reverb unit, usually has an average reverb time of maybe 1 to 3 seconds; the longer the reverb, the more "live" the room sounds. For a control room, you want a shorter reverb that doesn't hide what your actual recording is doing, or you will tend to add too much artificial reverb to your mixes and they won't sound right in a normal room setting.

John explains the basics of this on the SAE reverb calculator page, here -

http://www.saecollege.de/reference_mate ... m#verbcalc

This calculator only does normal building materials, but they are important in calculating the basic room response first - after that, you can see which frequencies need more absorption (the longer reverb times will be at those frequencies) - this tells you what kind of materials you need (and how much) by their absorption characteristics... Steve