How to Build a Soundproof Box for a Generator DIY (Step-by-step Guide)

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Do you live in an area where power outages are common? Or are you a camping/RVing junkie?

You will agree with me that generators are a godsend.

The only problem?

Generators are loud. I mean, like really loud.

You could consider investing in a soundproof generator enclosure. I explored a few options and most of them were extremely pricey—I’m talking high three figures to mid-four figures.

That’s when I decided to awaken the DIY artist in me and create a soundproof generator box that’s not only inexpensive but also efficient in reducing generator noise.

You can follow the exact same steps to achieve the same.

Just a quick one before we do begin:

We also have a mega-detailed guide on some other ways to quieten a generator that doesn’t require building a soundproof enclosure. So if you don’t like getting your hands dirty, you might not want to miss out on this one.

Moving on:

Let’s dive right into it!

Things You Will Need: At a Glance

Medium-density Fiberboard

The primary material we will use to make a soundproof box

Mass Loaded Vinyl (MLV)

This will be the primary material that helps blocks out the noise

Green Glue

Used to glue and caulk the first layer of sound-deadening insulation; Also decreases vibrational noise

Ventilation Duct

Required for air intake, cooling, and exhaust

Foam Mats

Provide an additional layer of defense for blocking sound

Saw (Circular or Table)

Step 1: Take Precise Measurements

Obviously, generators come in different sizes, so you will need to make a generator box accordingly.

It’s incredibly important to take accurate measurements. Remember, think twice, cut once!

Here’s how to take precise measurements:

  • Using a measuring tape, measure the dimensions of your generator
  • To account for the soundproofing barrier installation and vents, add an extra 2-3 inches on all the sides equally.
  • Jot down the final measurements somewhere

If you have multiple appliances to accommodate—like compressor, pool pump, etc—adjust the dimensions accordingly.

Step 2: Cut the Sides and Top of the Soundproof Box

With the measurements by your side, you’re ready to start cutting your medium-density fiberboard now.

You could try using regular plywood too, but in my experience, it is much less effective than a medium-density fiberboard.

This MDF is what I used and can recommend. The medium-weight chipboard sheets are effective and inexpensive.

Here’s how to get started:

  • Label the measurements on the fiberboard using a pencil.
  • Use a circular saw or a table saw to make the cuts. Alternatively, you can have the lumber store do it for you.

Step 3: Make the Holes for Ventilation

Higher the vents on the box, the better.

Here’s how to do it:

  • measure the diameter of the ventilation duct
  • based on the above measurement, mark circles on a piece of fibreboard
  • we need to make two holes—mark the first one on the top, more towards one side rather than the center.
  • the other hole is on the opposite side of the first hole

Now put down your incomplete soundproof box and make sure that the four sides perfectly surround the top of the box.

Step 4: Install Mass Loaded Vinyl

My favorite material for insulating the box from noise effectively is Mass Loaded Vinyl.

If you’re looking to buy an effective and inexpensive MLV, I’d recommend you check the one from TMS. It’s 1/8th of an inch thick and comes with an STC rating of 27.

Not sure what STC means?

STC ratings essentially measure how well a partition attenuates airborne sound.

You should leave some free space. By keeping these gaps, the sound can scatter inside the box and can be absorbed completely by the sound dampening material.

Here’s how to glue and caulk the first layer:

Step 5: Add Other Layers of the Soundproofing Material Inside the Box

The more the number of layers on the walls of the box, the more effective will it be in sound reduction. Hence, to make the insulating layer even thicker, you can add some foam mats.

Foam mats are soft and have sufficient thickness to absorb all the vibrations heading in their direction. They reduce the noise level by eliminating reverberations inside the box.

This extra-thick foam mat from ProSource is made from high-density EVA foam and is also water-resistant. It’s originally made for a cushioned work-out flooring for home and gyms, but you can use it in your soundproofing endeavors as well.

You may also add rubber foam (vinyl nitrile, neoprene, EPDM, or SBR) padding in the second layer to further cut off the noise.

It is important to glue all the things properly to the surface of the box. Else, it may leave gaps and crevices which will hinder the desired output of making a noise-free box for the generator.

Step 6: Assemble the DIY Generator Quiet Enclosure

Now, we are all set to assemble all the parts.

By using nails and screws, fix the walls of the box around the ceiling.

In order to get easy access to the generator, you can also add some hinges. Using hinges will require you to make some necessary changes in the vent hose, though.

Step 7: Install the Ventilation Ducts to Your DIY Generator Soundproof Box

Proper air circulation and airflow are crucial for the overall health and functioning of your generator. Without this, the generator might overheat to such an extent that it might ultimately break down.

In order to avoid this, you should add ventilation ducts to allow the heat to disperse effectively and allow fresh air to reach the generator.

The more you add the ventilation ducts, the better it is for your generator. Sound waves get dissipated if they have a lot of obstructions in their way, hence, you may make a lot of bends while installing the ducts to further cut off the noise.

Now, put the hose into the holes that you made in step 3 and tighten them well. Having done this, you are all set to go!

Frequently Asked Questions

1. How Do I Stop My Portable Generator from Making Noise?

Here are a few tips to quieten your portable generator:

Firstly, you can make a soundproof generator box to dampen the noise. Besides this, getting yourself a new generator with the latest technology or relocating your generator away from your house can also minimize the disturbance that it causes.

Installing sound deflectors that work on the principle of diverting sound waves is another good alternative. Replacing the muffler and installing a rubber flap are also very effective methods.

You can also add fluffy mats, carpets, and rugs underneath the generator to perfect absorb and dampen the vibrations created by the generator. To further baffle noise, you may attach a pipe to the exhaust and dip it into the water so that sound vibrations completely decline.

2. Can You Put a Silencer on a Generator?

Yes! The exhaust creates a loud noise which causes a lot of trouble. You can suppress the noise created by the generator by fixing the silencer to the exhaust pipe.

3. Why are Inverter Generators So Quiet?

Inverter generators are quieter than other non-inverter generators because of their design and technology.

They reduce mechanical noise by generating power in three stages. Firstly, AC is produced, then it is converted to DC and then again back to AC. By doing so it can alternate the speed of the engine accordingly and create minimal noise.

Besides this, all modern generators are equipped with the latest technology and sound-attenuating materials which further baffle noise.

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