how much insulation to put in basement shop ceiling?

My work area is roughly 375 sq ft. and is directly below the living room and kitchen/dining room. Because of stuff already in the way of the joints, a drop ceiling would be inefficient. My joists are 9" deep and for the most part are all open.

I have read that high frequencies will travel right through the joists. To do the whole ceiling with R30 (9.5" thick) it will be around $350. This will leave no air gap though.

Should I go with a lower R value to get an air gap?

Also if the joists themselves will let high frequencies through, at what point are the uninsulated joist bays no longer the weakest link in the chain? In other words, is R30 even necessary or would there be no noticeable difference between this and, say, R15?

thanks,
DW

High density sound batts. But, I'd use ⅝ drywall. Ideally, ⅝ drywall on hat channel

thanks. with everything that hangs below the joists a ceiling would be impractical unless I went so low that I would have 6 ft ceilings...

sound batts are out of my price range.

Insulation and 1/2 cement board.

half inch cement board between the joints?

I guess what I am really wondering is should I go with less insulation thickness so there is an air gap between it and the floor or should I fill the entire 9" joist cavity?

Sound reduction is a multi faceted effort & sadly, just fiberglass (or even mineral wool) batts are not going to do much. They'll help kill some of the higher frequency sound, but the low frequency will go right through. You need mass, isolation and absorption. The topic is far too complex to cover in one post, but if you head over to one of the home theatre forums, there's a wealth of info there.

Yes what Frank said.... it's a complicated topic
If you are primary concerned with high frequencies (even some spoken voice) then fiberglass will help.... if you can fill the void completely with insulation that would be better
Insulation alone will not help for low frequencies

Sound isolation can be an crazy exercise in cost benefit analysis..... been there done that
If you want to go deep down the rabbit hole check out AVSforums

thanks Vince. Even if I wanted to get into doing the sound reduction thoroughly, the plumbing/dust collection/electric/lighting/etc are all in the way. I don't even consider this an option. It sounds like I will just have to live with a loud basement shop.

If 9" of insulation in 9" deep cavities will help more than 5.5" then I will go with the former.

Can you mention what you considered high frequency? Router table cutting? table saw running?

Dustin,

I was in more or less the same situation, except there were already papered fiberglass batts installed between the joists, but they did not fill the space effectively they only filled about 4½". So I bought more unfaced fiberglass to finish filling the space and I think it made a huge difference in the sound. Any noise from the shop is just background upstairs. Whatever size I bought I ended up having to split it in half along the thickness because it was about double what I needed, and our sLowe's is so defective they didn't have a thinner option without special order.

Thanks Charles. That is helpful. I would be very happy to achieve "background noise" status. The biggest culprit is my 12" table saw. With the blade off of it, you can hardly hear it running. Put the blade on and it sounds like a jet engine ready for takeoff...

My nephew used the blue denim insulation Menards sells to go between the first floor and the basement. He has 5 kids and they are noisy in the basement. He said the blue denim is best for sound.

Quote:

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Originally Posted by dustin wassner

thanks Vince. Even if I wanted to get into doing the sound reduction thoroughly, the plumbing/dust collection/electric/lighting/etc are all in the way. I don't even consider this an option. It sounds like I will just have to live with a loud basement shop.


If 9" of insulation in 9" deep cavities will help more than 5.5" then I will go with the former.


Can you mention what you considered high frequency? Router table cutting? table saw running?

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I would consider higher frequencies as 250-500Hz and above
Not sure where specific tools fall in the Hz range.... I tried a quick google but no love
You will hear a difference but it will not eliminate all sounds

Rabbit hole:
Regarding different types of insulation.... extensive research has been done and an excellent resource is http://www.bobgolds.com/AbsorptionCoefficients.htm
Note: thicker "pink" is very similar to more expensive items like safe and sound
Unfaced 6.25" R19 on wall..........................0.64 1.14 1.09 0.99 1.00 1.21 1.05
Safe‘n’Sound 3" (75mm) 2.5 pcf (40 kg/m3) 0.52 0.96 1.18 1.07 1.05 1.05 1.05

I don't see denim on there (might have missed it) but I can't see it being much different that ruxol safe n sound