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How I’m Soundproofing My Shop Part II

Soundproofing-Isolation with Caulk

Doing some simple things when you’re installing drywall like sealing your stud bays, adding radiant barriers, foam insulation, or decoupling your drywall from the structure can make a big difference in your acoustical and thermal comfort .

In the last post, How I’m Soundproofing My Shop Part I, I explained how I break down my sound abatement strategy to both limit the sound coming from my tools and limit the sound allowed to escape the shop to bother others.

I just categorized the approach like this:

 Sound Source Control

 Sound Escape Control

I described exactly what I’ve done (and am still doing on a few machines) to control the source of all the noise, right at the tools.  Now, I’ll walk you through how I prevent the leftover noise from bothering family members and neighbors (and you, too).

This is your last line of defense, so make it good.

Sound Escape Control

Controlling sound escape means somehow blocking or absorbing the sound within your shop so it never leaves the shop envelope, basically your sound bubble.

Create an Air-Sealed Envelope

The most important and effective thing you can do is air seal your shop envelope.  I mean totally seal it off; floors, stud bays, around outlets, and ceilings.  Don’t forget to account for fresh air or it’ll get awfully stale in there.  But if you can do it mechanically, or at least use a sound-insulated lined sheet metal duct to the outside, it’s better than a plain louver in your wall.  Just make sure you don’t have a line of sight from a fresh air intake to the outside; use a long serpentine shaped duct instead, and line the inside with 1” sound insulation.

If you go through all the effort to sound-insulate your shop only to have holes in the envelope (leaky door seals/ weatherstripping, combustion air vents, leaky windows) you’ve wasted a lot of time.  Sound travels readily through air, so you don’t want to be on the outside of your shop (or worse in the house) and have given the air a way to freely transmit that sound without interruption.

Do these things to your shop bubble:

      • Seal each stud bay separately
      • Make sure any top plate penetrations are fire-caulked
      • Seal bottom plates to the foundation
      • Use special drywall, such as QuietRock
      • Caulk all drywall corners:  ceilings, floor, adjacent walls, door frames
      • Weatherstrip your doors, including the threshold
      • If you have a roll-up garage door, do your best to align the side seals
      • Buy a rubber, squishable bottom door-seal for your roll-up door
      • Add weatherstripping/ gaskets anywhere you can between roll-up door panels & seal even small holes
      • Seal your shop’s window frames
      • Add gaskets around your outlets and switches under the decorative plates
      • Do something about wall/ roof openings with a direct line of sight to outside (louvers); install a “sound boot”, which is an insulation- lined duct elbow
      • Add sound putty around outlet boxes
      • Window-mounted or thru-the-wall PTAC (packaged terminal air conditioning) units allow sound to go right through your walls.  Consider a split system unit so you only have refrigerant piping going through your walls, which you can seal
      • Seal any duct/ pipe/ electrical penetrations throughout

Of course, these measures will have thermal benefits as well.  You’ll be much happier with your ability to heat the shop and keep it warm with little energy.

Appliances in the Shop

In my shop, I have a water heater in there.  It’s a gas-fired unit, so it needs combustion air.  Right now it’s open to the shop, which is bad because a dusty environment plus a gas flame can’t be good.

My plan is to enclose the water heater completely, but now I’ll need a source for combustion air intake.  How you do this is defined by your local building codes (usually under Mechanical).  For me, I’m following the California Mechanical Code.

So, sizing per this code, I’m adding combustion air louvers toward the outside, with the water heater enclosed in closet and sealed off from the shop.

WoodChip Tip: Doors are notoriously hard to air seal.  If you have a door leading to your house from your garage or basement shop, or an exterior door, really consider using an airlock type system using two doors.  You can either have the two doors separated by a foot or so, or you can create a vestibule or “mud room” element.  This will help keep dust out of your house, and will do wonders for your sound blocking efforts.  See below for what this will look like in my shop. 


Soundproofing Your Shop Doors

My door plan. The goals of this design are: Fire, Security, Sound, and Thermal protection. Note the wedge-shaped jambs and threshold; these help the kick-resistance of the door, and also eliminate a line-of-sight opening into the shop.

Assuming you’ve air-sealed your shop to keep sound from escaping the “easy way”, you can think of your overall strategy as reflecting & blocking sound, preventing sound transmission, and absorbing sound.

This means carefully designing your wall and ceiling layers, thinking about your door system (yes, system!), window system, ventilation, and floors with sound reflection, absorption, and vibration transmission in mind.

Carefully Design Your Wall and Ceiling Layers

Each of your loud tools has a range of frequencies, and a dB (noise level) associated with each frequency.  So you have to incorporate design strategies to mitigate both higher frequency ranges as well as the lower octave bands.

You don’t really need to get too deep into the science of it, but you should understand what different types of materials do, and how best to employ them.

Different materials you use for your walls, ceilings, doors, and floors have sound absorbing, sound transmission, and sound-reflecting properties (how the various frequency bands affect it).  Of course you can’t have a wall made entirely of insulation, or it would have a tough time supporting your roof.  So you will need to consider the various materials you plan to use, and how they’re layered and adhered to each other.

Soundproofing Shop Walls

My wall design is geared toward both thermal and acoustical protection, both for myself and my neighbors.

Lower Frequencies and Vibration

Assuming you’ve done or are planning on doing the things mentioned in the last post to lessen tool vibration, the remaining noise that strikes your walls, floors, doors, windows, and ceilings will vibrate those materials.  Your goal is to keep those vibrations from reaching the other side as much as possible.

Most sound-absorbing insulation is good at mid-to-high frequency ranges. Lower frequencies are harder to attenuate, and require a heavier mass material.  It’s up to you as to how far you go, but I’m finding that for reasonable amounts of money, spent smartly, I can be highly effective.

Materials in direct contact with each other will transmit the vibration from one side of the wall to the other, effectively creating a sound-transmission path.  So even if you don’t want to spend much money on things like mass-loaded vinyl (designed specifically for low-frequency sound attenuation), or Acoustiblok, you can stop much of it from going through your wall via direct vibration transmission.

What I like to do is decouple at least one layer to minimize the direct contact with the structure.

One way to do this is to build two walls right next to each other, with a 1” air space between them.  Another way of doing this is to use construction adhesive, Green Glue Compound, or my favorite, dry caulk “squiggles” on the studs before I install the drywall or other layer.  Still another method is to use resilient drywall channels, or better yet, “sound clips”.  These are z-shaped cross-section metal strips that you screw the drywall to.  Another part of the channel is screwed to the studs, creating a bit of a spring-cushion.

Basement ceilings will benefit tremendously by decoupling.  Even if you have dropped “acoustical” ceiling tiles, adding a decoupled layer of drywall somewhere (using resilient sound clips) will give you better lower frequency performance.  Be sure to attach the sound clips directly to the joists.

Soundproofing Shop Framing

Here I’m using firecaulk as my cushion between my drywall and the studs. I’m purposely allowing the foam insulation in-fill to protrude a little bit so that the drywall has a flush surface.

WoodChip Tip What’s weird is that a “double wall” with gyp. board only on the outside layers performs better (better STC rating, see below), as opposed to ALSO having gyp. in the “inside” airspace between.  You can read more on the “triple leaf effect” at  On my wall between the house and the shop, I want to leave the original fire wall intact, with gyp. on both sides.  However, with the second decoupled wall I may put drywall on the side facing the interior of the shop and omit the inside layer.  I’ll still fireblock at the top for the whole thing, though. 

Lower frequencies are best absorbed by dense materials.  They make mass-loaded vinyl products, Acoustiblok sheets, or you can look into using cement board.  I just plan on adding two layers of drywall separated by dry caulk squiggles.  One layer will be ½”, and the other will be 5/8” so that each resonates at a different frequency.  I figure there’s enough mass/ density there to do what I need, and I have a 1-1/2” thick cement stucco scratch-coat layer on my wall’s exterior.

The more you can mimic a “room within a room” the better your design will perform.

Garage Roll-Up Doors

On my roll-up door, I can’t add anything too heavy or the motor won’t be able to lift it.  Since it’s made of sheet metal, I may spray the inside with a sound-dampening coating to lessen the vibration in addition to adding foam insulation panels.  Also see the post about the thermal comfort , specifically the section on insulating the garage doors.  In my climate, it’s a no-brainer to have an airspace and radiant barrier foil at these insulation panels.

If it’s a really critical thing for you, you could purchase heavy sound-absorbing curtains and simply draw them closed in front of your roll-up door when your shop is in session.  I may add something like that later on if I have the money.

Soundproofing a Garage Door

Whether you have a sliding barn door or a roll-up door, you can add a sound-absorbing curtain in front of it. My current door is a roll-up type, and I’m adding foam radiant barrier panels covered with cloth for aesthetics. But that doesn’t absorb sound too well, and besides sealing the frame edges, I think this would help reduce what the neighbors hear quite a bit.

Mid-Range and High Frequencies

Sound insulation, soundboard, and certain types of foam typically are good in the mid to high frequency range.  You could look up the sound attenuation properties of different materials in each octave band, say the 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, and 8000 Hz frequency ranges, and see how much (in dB) reduction you get in each octave band.

Or, much more simply, you can Google STC rating (Sound Transmission Class) of various wall systems, or read sites such as  The higher the STC number the better.  The way to increase your STC is use the techniques above, namely decoupling layers, adding mass, and adding materials that absorb sound.  I would target an STC in the 60-range.

Now, be careful in that STC isn’t used for evaluating how much lower frequency noise is vibrationally transmitted  through your wall.  Take care of that by decoupling your layers and adding mass.

Soundprooing Around Electrical Outlets

It’s critical that even pinhole leaks are sealed to get the soundproofing you want. I’m sealing all the sill plates, top plates, stud bays, and any other penetration by piping and wires.

Extra Credit

If you have a particularly loud machine near a wall, you might want to provide an extra sound-absorbent panel right at that wall.  Cloth-covered panels, or special sound absorbent products would be good here, since it’s in a limited application and won’t get too expensive.

It probably can’t hurt to plant some foliage next to an exterior wall between you and your neighbor.  I’m doing that more for the cooling/ shading effect, but I’m sure there’s some sound absorption there.

Another thing I’m doing is adding a Lexan (a clear plastic material) panel to the inside of my window, with a hinge and latch, and gasket all around.  This will have a thermal (and a bit of security) benefit as well.  If you’re adding a window to your shop, get a dual-pane, Low-e model. For not much more money you’ll enjoy the benefit of its solar and acoustical performance.

Soundproofing A Window

Currently I don’t have any windows in my shop, but I’m going to add a few. I’m thinking round porthole windows because they look cool. I want some natural light, and I also like to be able to look outside (sometimes you hear a loud noise and it’s nice to be able to see if your neighborhood is on fire). But windows present a thermal, security, and sound problem which can be solved through design.

Sound Reverberation (Your Own Sanity)

Taking measures to reduce the sound heard by your neighbors and family is very nice of you, but while you’re at it take care of yourself too.  Avoid highly sound-reflective layers as the final inside layer.  You don’t want sound bouncing all over your shop and back to you.  Having a sound reflective layer within your envelope will help keep sound from escaping, but back it on both sides by absorptive layers.

Also, taking a cue from theaters, you can suspend cloth-covered soundboard or acoustical tile panels either vertically or horizontally in your shop to interrupt reflected sound as it bounces around.  These are an effective way to baffle sound within your shop.

In my previous post, Smithy commented that having non-90 degree corners can help with sound amplification, or at least the perception of it.  If you’re standing at a loud machine (which is usually where you’ll be while it’s on), that tool is sending soundwaves out that hit the corners of your shop.  90 degree corners reflect this sound directly back to you.  This is because the angle of incidence = the angle of reflection.  Notice that stealth aircraft don’t have tail surfaces 90 degrees to each other.  This is because if a radar wave hits the vertical tail at any angle, it’ll bounce off that and the perpendicular horizontal tail and back to the source, thus allowing detection of the plane.  So, maybe think about making your ceilings at non-90 degree angles to your walls for both decorative effect and sound reasons. Notice the Lexan panel on my window design above.

Soundproofing Concepts-Angle of Incidence Equals Angle of Reflection

The Angle of Incidence = Angle of Reflection. No matter what angle you hit a wall with a light beam, soundwave, etc., it will reflect off at the exact same angle (if it's a relatively flat wall) in the same plane. Now, in a 90 degree corner situation, this reflection hits the other wall at the 90 minus the original angle, and reflects off of that 2nd wall. This "90 minus Original Angle" happens to aim right back atcha! Stealth designers know this, that's why you don't see panels at 90 deg. angles to each other on those aircraft.

Are These Things a Part of Your Design?

Below are the main things to do to your shop’s shell:

        • Buy lots of caulking and spray foam and seal everything inside your walls and ceiling.  Good for keeping ants out, and helps your shop keep temperature too.
        • Weatherstrip around your doors, including the bottom threshold.
        • Build your shop around any household appliances that have to stay; try to keep them walled off and access sealed.  Provide required ventilation via the outdoors or duct it.
        • Plan your wall layers taking into account thermal comfort, sound, and security.
        • Decouple wall surfaces that absorb your machine vibration from the shop structure.  Isolate things that generate or absorb sound.
        • Deal with the elephant in the room first; things like super-leaky garage roll-up doors, uninsulated basement ceilings, single-pane windows.
        • Make sure you’re both absorbing sound and blocking sound from escaping.  Reflect sound back into an absorbent material on purpose.

Remember that a lot of little things will add up to a much quieter shop.  Or you can just hand out hearing protection to all of your neighbors and family…

For more guidance in assembling your Woodshop Design, click on the Starting? Go Here! category and read those first.

Connect with me on Facebook, and follow me on Twitter for more ninja tips to Optimize Your Woodshop!

And, if you’re on Twitter, be sure to follow #woodchat every Wednesday night, at 6:00 pm, PST.

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6 Responses to “How I’m Soundproofing My Shop Part II”

  1. Bill says:

    I have 3hp cyclone in 90 degree corner with triple brick walls and i want to lessen noise from motor and from reflection off walls. Advice?

  2. Michael Palma says:

    I came across your site from research I’m doing on soundproofing my roll-up garage door. I have read for hours and have run across little that states specifically all of the products a person has used to reduce noise heard by neighbors. For me this is critical considering my communities HOA (and the half-dozen or so how nazis 🙂 ). I was considering adding heavy mass vinyl sheeting to my (already installed ) RTech Insulated panels, but am not sure if it would help considering the product states it was designed to put between drywall panels. Any thoughts? Love the site btw 🙂

  3. Wow, what a detailed write-up. I’ll have to think about noise insulation if I ever have a house custom built! I’ve been obsessing over trying to “silence” my shop vac for a while – got it a bit quieter with some panelling and this muffler made out of foam. There are better ways I’m sure, but I ended up doing most of my stuff with scrap materials, so I can’t complain.

    • Bobby says:

      That looks pretty useful; the shop-vac muffler I have reduced the sound a little bit but only for some frequencies.

      The way things like sound attenuators (sound traps) for HVAC applications are rated, they take multiple octave bands (125 Hz, 250 Hz, etc.) and evaluate how much dB was knocked off at each frequency range. Typically the lowest frequencies are hardest to attenuate and mid-ranges are easier. Mass-loaded vinyl is one material you can use to reduce lower frequency noise.

      The thing I worry about is pressure drop; luckily shop vacs have high suction capabilities (and low air flow, CFM) whereas dust collectors have lower suction capability but high airflows.

      You can also try wrapping the shop vac itself, and look at using neoprene/ rubber washers at the motor-mounts. Just make sure the motor-cooling airflow isn’t blocked too much, though. I wish they would build in more sound-absorbing features into these screaming things.

  4. Bobby says:

    Thanks, Dale! Let me know if you need any help or if you have any ideas that’ll help everyone.


  5. Dale says:

    I’ve been thinking about sound proofing my workshop too, thanks for the tips.

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