I am new to the CNC routing world and am currently researching the best way to design a soundproof booth for my new 4 x 8 CNC router. In my research I have found that staggering the 2 x 4 framing on say a 2 x 6 or 2 x 8 sole plate will create the much needed airspace to help deaden the router sound. On each side of the wall I considered using GP Hushboard (sounddeading board found at a local lumber yard) and 5/8" gypsum on top of that (both on the interior part of the wall and exterior).

I have also read that fiberglass insulation offers no soundproofing qualities and either does "eggcrate" material.

Does any one have any tips for my dilemma?
Thanks in advance!

What you are describing is the standard way to build a sound isolating wall. The staggering is not to create an airspace it is to physically separate the two wall surfaces so that vibrations are not transmitted via the wood frame from one gypsum board surface to the other.

An idea I had, but have not tested, is to put acoustic ceiling tiles facing inwards on the walls underneath the gypsum board. The theory behind this is that any sound that does penetrate into the wall cavity will be largely absorbed by these tiles rather than transmitting through the gypsum board.

I would imagine also lining the room, walls and ceiling, with the same tiles would help diminish the sound level also

That sounds like a great start. To make it even better, attach the gypsum to the sound board with green glue. heres a link http://www.greengluecompany.com/ it is a sound deadening construction glue.

in absolute mode can get real expensive (theres a sheet rubber material)
but if your local lumber yard has sound deadning board (looks like flaky mdf with strands) or place your outside sheetrock first then skin inside with cieling tiles, look for removed material from a building (office upfit)
you also can offer to remove it for free!! then insulate walls and shin interior
with 1/2" sheetrock or ply the sound chaulk is a good idea

oh and i hope your doing this for a neighbors benifit

mine is got one wall of cmu and we can barely hear it with the door open

we've had to do the sound thing a few times' the mohogany theater below is right below the owners bedroom, (kids on video games after midnight are like
listening to a war with a $40.000.00+ set of speakers

geof is absolutly right about staggered studs

cabnet

EAR MUFFS. (LOL)

Thanks for all the good advice. We may try the acoustical tile trick on the inside walls. I did read about the green glue as well, which makes sense to create a barrier for the vibration between the stud wall and the two layers of sheathing material. I'll let you know what happpens.
regards,

Use a router with a lower DB output like the Hitachi M12VC.

http://www.tylertool.com/hitachi15.html

EAR MUFFS. (LOL)

Darn i was going to say that until I scrolled down and saw this.

sound diminishes by the square of the distance. so don't use walls, just move the router further away. but seriously...
closed cavities will resonate (a wall lined on both sides with air gaps inbetween)
mass absorbs sound. you might find the cheapest solution is to line one side, and pack old newspapers (100% dry of course, not damp ones from the garage) in the cavities before lining the other side. Fibreglass or even special 'acoustic blanket' just doesnt have the mass to absorb much - they are generally for 'treating' the acoustics in a room by aborbing the high frequency sounds and preventing reflections (echo). same for acoustic ceiling tiles.

At the end of the day, mass beats any other 'trick' at deadening sound - so use precast concrete walls or brick and mortar!

i know a fair amount about sound... a lot more about sound than i do cnc which is why i sold off my cnc router and outsourced my cutting to someone else!

the sound you're getting is mostly high-end noise from the cutter. the router motor (while noisy) is pretty much overwhelmed by the cutter noise. there is a LOT of energy in that noise! the structure you'd need to build to really get rid of the noise would be crazy-heavy. and even having small sections like windows or doors that are not isolated like the walls will let a surprising amount of noise leak out. you will have very little success with acoustic foam. i am telling you this from actual measurements and knowledge. you'll burn a lot of money and it won't work for this application. acoustic foam is great stuff but not for this spectrum of noise.

essentially you can choose one of two routes - you either try to stop the noise from travelling out or you try to just dampen/muffle it down to an acceptable level. the good news is that for this kind of noise, you can probably dampen it pretty effectively. while many people here are correct that nothing beats mass in defeating sound, the density and mass becomes more important the lower the frequencies - and this noise is not too low frequency.

my advice in terms of cost effective, and manageable, would be to use a cavity-filling polyurethane foam like handi-foam or similar and fill the wall cavities. use 3/4" drywall on both sides of the wall. use a solid cavity fire-rated door into the room and avoid any windows. this will give you a very reasonable amount of acoustic blocking without expensive materials or extremely heavy structures. will it be soundproof? no but it will significantly reduce the noise. will it be better than x, y or z? hard to quantify because there are so many ways to attack this kind of problem. but it will be a very cost-effective approach and almost always gives excellent results for this kind of sound.

good luck!