Dave Grohl - Soundproofing

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Hello Black Leaves of Envy,

I read the news story and watched your great video and in it could see

glimpses of your garage practice space. With its block walls, concrete floor,

open ceiling and roll up door it is like a perfect speaker box for projectingyour music to the distant neighbors, they should be grateful, but since they

are not, here is a few things you can do help quiet down whats getting

outside.

  The biggest change you could make would be to fill the block walls with

sand, this would help trap some of the lowest sub frequencies that travel

the farthest. With the ceiling open you could get easy access to the top of

the blocks and then literally pour in sand until they are full.

  Cover the ceiling, 2 layers of drywall would help a lot but anything you

can find will make it better, plywood, house siding, etc, as many layers as

you can.

  Fill large garbage bags with blankets, clothes, old socks, packing peanuts

most anything, dense and fibrous is best. Stack these on top of each other

in the every corner of the garage, floor to ceiling, they will act as corner

traps and help with low frequencies that build up in the room.

  Add mass to the roll up door. This could even be leaning sheets of

plywood and mattresses against it.

  Add mass to the walls, hanging blankets, carpets, mattresses everything

you can find, the thicker it is the lower frequencies it traps.

  cover the floor in rubberized material, carpet pads, gym mats, rubber

back entry mats.

If you are interested in more about Sound Proofing and Sound Treatment

here are some of the basic principals and materials used.

There are 4 primary ways to soundproof.

Add Mass or Density

  Many ways to do this, using concrete board, drywall, mass loaded vinyl,

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plywood, sand etc.The most common way is to add another layer of drywall over the roomsexisting drywall, the soundboard and drywall combination gets great resultsas well. For major reductions you might have to layer some concrete board

and mass loaded vinyl.

Dampening

Damping means to reduce resonance in the room, by absorption orredirection (reflection or diffusion). This is commonly done with variouskinds of insulation, Rockwool and semi rigid fiberglass being the mostcommon.Sound Board, Sound Board, Sound Board… or as it is also called, FiberBoard, is a rigid panel produced from non-toxic organic material and natural

wood fibers that are wax impregnated which is lightweight, cost efficientand easy to install, this stuff is your best friend for tonally tightening up yourspace and quieting things down, made by many manufacturers and sold atmost hardware stores, usually runs $10–12 bucks for a 4’x8’ Sheet. youcan glue it, screw it or nail it to just about anything, stack it or arrange it todeal with different frequencies, it is not a cure all but is one of the best bangfor your buck in sound treatment.

Decoupling

  Decoupling means mechanically separating the two sides of a wall tomake it harder for sound to pass through the wall. This is can be done bybuilding double walls or with rubber boots and pads to set walls and joistson. Resilient channel can be used to add space and separate contactbetween wall or ceiling panels. Any material with and air gap between them(decoupled) will stop more sound transfer than the same material makingcontact.

See images below:

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Sound Treatment

  When it comes to treatment of a room there is a common equation of

30%, 30%, 40%, which means, 30% absorption, 30% diffusion and leave

the rest in its natural reflective state. This works good for recording studios

but when it comes to the rehearsal space or jam room you may need to

over compensate in some areas as these are rarely rooms designed for

sound and usually have many unique sound traits.

Spectrum Analyzing

 Before you start it helps to know what you are dealing with. this has

become easily accessed technology. From your smart phone you can

generate Pink noise or individual tones to run through your PA system, as

well there are some good spectrum analysis apps that will be calibrated to

your specific phone. Neither of these will be perfect but are a cheap and

easy way to get a good idea where the problematic sonic issues are in

your room.

http://i.imgur.com/AEeYzUE.jpghttp://i.imgur.com/4pMKx8K.gifhttp://i.imgur.com/mP6dNOG.jpg

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Corner Traps

  Lets start with the most common scenario. You have a square or

rectangle room that sounds boomy or cloudy when you play. Low frequency

energy will build up in the corners of the room, to clean this up you need

some bass traps. A simple way to apply this is get 8 large bags of deniminsulation and stack the on top of each other, 2 in each corner. Use twine

and screws to keep them tight in the corner, hang a blanket in front if you

want. You will be amazed how much this will tighten up the low end in your

room. Fiberglass insulation is cheaper and will work as well, but is a lung

and skin irritant. Please wear gloves, long sleeves and a N95 particulate

mask when handling it. if you want to build some corner traps here are a

few designs, there are multitudes of them listed on the web all with the

same basic concept.

  A simple and cheap way to build a corner is to come off the corner about

18” in both directions, there anchor 2”x2”s into the walls from floor to

ceiling, cut 2 pieces of sound board to span the corner at a 45 degree

angle, roughly 4’ by 30”. start from the floor up, screw the first piece of

soundboard across the corner into the 2x2s. Then you are going to want to

fill the space behind it with denim insulation. When the lower 4’ is full cut

the upper panel to leave a space at the top, attach and fill, repeat in allcorners.

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Sound Diffusion

  Now that your corner traps have cleared up the low end, you can think

about diffusing your parallel walls. Anytime there are large parallel surfaces

you will get reflection resulting in standing waves and room modes. In most

rehearsal situation a few layers of soundboard will help deal with this on the

absorption side, but a combination of absorption and diffusion will create a

more sonically balanced room. Here are some examples of diffusers.

Low Budget Options

You can build a great dense diffuser with 2x4s and a sheet of plywood or

with some cedar boards as well as applying siding to sections of the walls.The siding will help deflect the frequencies at an angle. Seen first below is

the normal installation, you may want to flip that upside down and install

from ceiling to floor which would then deflect sound to the floor rather than

the ceiling.

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Floors to Ceiling Reflection

  The same principals of corner traps and diffusers apply to the ceiling,

though when hung from the ceiling they are called clouds.

If you are interested in learning Everything about acoustics, here is a link to

a free PDF version of F. Alton Everest’s book Master Handbook ofAcoustics. http://bit.ly/1Rw4MTA