How To Block Low Frequency Sound Waves (Bass)

How To Block Low Frequency Sound Waves (Bass)

While any form of noise pollution can be annoying, low frequency sound waves (bass) are some of the worst. They travel much farther and through thicker objects, leaving many of us wondering how to block low frequency sound waves. Here’s a quick answer:

When it comes to how to block low frequency sound waves (bass), your best option is a combination of mass and sound attenuating materials. Bass requires more materials to block than higher frequencies, but using plenty of dedicated soundproofing materials will solve the problem.

In this article, I’ll look at some specific information about why bass frequencies are more of a problem to solve, along with the most effective solutions for doing so.

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What Are Low Frequency Sound Waves?

Low frequency sound waves typically cover the 100-150Hz range and are, for example, the type of waves that come from a stereo subwoofer. However, many noise sources produce bass frequencies.

Sound waves are caused by vibrations, either through the air or solid materials. For sound waves to exist, they need a medium to travel through, which is why there’s no sound in a vacuum.

Hertz is a unit of frequency, and sounds have a wave pattern that corresponds to different frequencies. Pitch is the unit of measurement that refers to how the human ear hears a sound wave.

Higher pitch sound waves operate at a higher frequency, while bass frequencies correspond to lower pitch sounds.

Sound waves use energy when they travel, and this energy is gradually lost as the sound waves cause air particles to vibrate. This is why sound waves can’t travel indefinitely.

Low frequency sound waves can travel farther than high frequency waves because they don’t use as much energy in the process. They transfer less energy to the medium they’re traveling through, meaning they can reach greater distances than high frequency waves.

This is true for both travelling through air and solid materials. High frequency sound waves are more easily blocked by heavy materials because they lose their energy faster.

Low frequency waves, however, cause fewer vibrations in the material and so can pass through more easily. Therefore, you need heavier and thicker solid materials to effectively block them.

While this logic helps when sounds, such as fog horns, need to travel massive distances, it’s not very helpful when it comes to soundproofing against unwanted bass noises in your home.

There are plenty of sources of bass frequencies, including:

  • Road traffic (cars, buses, trains, etc.)
  • Household appliances (washers, dryers, boilers, etc.)
  • Music
  • Construction sites
  • Electrical appliances and substations, etc.

Luckily, it’s possible to combat many of these with soundproofing solutions. But the effectiveness of your options will depend on the proximity of the source to you, and its volume.

Checking For The Noise Source

The first thing to do before trying any soundproofing solutions is to find the source of the noise as best as you can.

While you might not be able to pin it down exactly, if it’s coming from inside your home it shouldn’t be too difficult. Start with these steps:

  1. Is it coming from outside your home? Listen at walls and windows to check if the sound is travelling through. Your walls might even vibrate slightly.
  2. If not, check around your home for any appliances in use. It might be a washer or dryer, or a boiler.
  3. This is easiest to check by turning them off and seeing if the noise stops.
  4. If it doesn’t, the source might be something harder to check, like pipes.
  5. Is it a neighbor? Is the noise source localized to one side of your house?

The more effectively you can narrow down the noise source, the better your soundproofing solutions will be.

Importantly, soundproofing against bass can become expensive, so you’ll likely want to be as efficient as possible.

Localizing the noise source to something like a boiler room or specific appliance cuts down on the work needed.

How To Block Low Frequency Sound Waves Or Bass

Here are some ways you can block bass or low frequency sound waves:

1. Add drywall as a sound barrier

drywall

Bass can vibrate further through solid structures, so adding more mass to them reduces its ability to do so. While drywall isn’t the heaviest material, it’s readily available and inexpensive.

If the noise source is localized to a single wall in your home, add a layer or two of extra drywall to increase the mass and thickness of the surface. Use some Green Glue (Amazon link) to sandwich the layers together for extra sound dampening.

You can buy soundproof drywall for this exact purpose. It contains an extra layer of sound dampening materials, along with more mass. This will help you to cut down on the amount of material you need to attach to the wall.

2. Decouple the wall

A more effective option, providing you’ve got the time and skills, is to decouple the wall. Decoupling basically means isolating both sides of the wall from each other, meaning sound waves are prevented from passing through.

You can either use staggered studs or double studs, both of which contain a layer of high-density insulation in between. Double studs require more work and will mean basically taking the whole wall down.

However, when it comes to bass frequencies, this is probably the best option because they can be problematic waves to control. You can find a simple video tutorial on what is decoupling for more information.

If you don’t have the resources to decouple a wall, consider using resilient channels instead. These isolate the drywall from the studs, basically giving the same results for less money.

Combine resilient channels with appropriate cavity wall insulation and you should have a fairly effective solution for blocking bass frequencies.

3. Insulate any wall cavities

Wall cavities are a soundproofer’s enemy. The empty space can trap sound waves and is perfect for reverberation, which can amplify the sound waves. This is why bass from your neighbor’s sound system can sound louder than it is.

Filling the cavity with some dense fiberglass insulation is a great way of solving this problem. The fibers are packed in a random pattern into a thick and dense material, which is perfect for this job.

The material’s density effectively dampens sound waves and prevents them from passing through the wall. It also fills the empty space, which cuts down on echo and reverb.

While this option alone might not completely block bass frequencies, combining it with some resilient channels or decoupling will do a pretty good job.

4. Use an isolation box for small appliances

If the source of bass frequencies is a small appliance, such as a computer or even a boiler, an isolation box could solve the problem.

While these are designed for acoustic treatment in home recording, they serve this purpose fairly well. After all, they’re designed with soundproofing in mind, and that’s what we need.

An isolation box should provide around 30dB of noise reduction and will help to dampen bass frequencies.

However, its size means it won’t be a viable solution for bigger or louder appliances. This’ll be an affordable solution for small annoyances, such as loud appliance fans.

5. Build a DIY window plug

window plug

While soundproofing a window on its own likely won’t solve all your noise problems, it’ll potentially make a big difference.

Windows are one of the weakest areas in the home when it comes to noise infiltration. This is mostly because they’re thinner than walls, and so let sound in more easily.

A simple solution to this is to build your own soundproof window plug. For this you’ll need:

  • Some lumber
  • Mass loaded vinyl
  • Acoustic foam
  • Green Glue
  • Nails
  1. Measure the size of the window, including height, width, and depth. Be sure to leave an inch or two clearance between the plug and the windowpane.
  2. But it must also be about 1” wider on the sides to create a tight seal around the window frame. Factor this into your measurements when building the backboard.
  3. Measure out pieces of MDF the same size as the back and sides. This is the base of your frame.
  4. Cut a piece of MLV the same size as the backboard.
  5. Glue down with Green Glue or other bonding material.
  6. Cut a piece of acoustic foam the same size and stick down, leaving a gap around the edge to fix the sideboards on.
  7. Stick the sideboards and nail in place for security. These should fit into the depth of the window frame, leaving a small amount of clearance.
  8. Attach some handles to the back and you’re done.

This is a pretty effective solution for blocking bass frequencies coming through windows because it adds mass and sound dampening to this weak area.

What’s more, the small gap between the plug and window creates dead air, which traps sound waves and prevents them from reverberating.

The major drawback, however, is that it completely blocks light. For this reason, you’ll probably only want to use it at night, but at least you’ll sleep better.

6. Use soundproof curtains

Soundproof curtains shouldn’t be your main choice when blocking bass frequencies, but they’ll definitely help. Check out my recommended soundproof curtains.

Focus mainly on weak areas, such as doors and windows, but you can also hang them in front of walls if you need to.

They differ from normal curtains because they have an extra layer of sound dampening material in them, which makes them thicker.

Granted, they’ll be better at blocking higher frequency sound waves, but they will make a difference to bass too. You’ll notice this more with quieter bass sources.

Go as thick as you can for the best results, but don’t expect miracles. That said, they’re a fairly cost-effective solution that’s not particularly invasive.

7. Be sure to seal any gaps around the home

You should never overlook the importance of properly sealing all gaps and cracks around your home. While this won’t do wonders on its own, it’ll still make a difference.

Sound waves act much like heat: they can enter and escape through even the smallest spaces.

What’s more, a crack between a wall and window creates the potential for more vibrations, which can amplify bass frequency waves. Blocking this gap will prevent this from happening.

Your 2 best friends for this job are weather stripping and acoustic caulk. Weatherstripping is designed for sealing small gaps around doors and windows to improve thermal insulation. But it works well for soundproofing too.

Acoustic caulk is a great material that converts sound vibrations into heat energy. Unlike normal caulk it’s much more elastic, meaning it’ll adapt as the building shifts over time.

Combine this option with a number of other soundproofing solutions and you should have a fairly effective barrier against bass frequencies, no matter where they come from.

8. Install some bass traps

 

Bass traps are specially designed pieces of acoustic foam that work against low frequencies. Their structure and composition is slightly different to normal acoustic foam, and they often sit in the corner of a room.

Bear in mind, though, that they’re designed to stop bass escaping a room rather than entering it. They dampen bass waves to reduce echo and reverberation, so might not be the solution you’re after.

However, they’ll be useful if, for example, someone in your home plays loud music (or TV) and you want to work in a room nearby.

Buy a pack of 4 and stick them up in the corners of the room. If you combine this with some heavy-duty curtains then you should end up with a solution that effectively blocks the bass coming from an adjoining room.

Some Final Thoughts

When it comes to how to block low frequency sound waves, your best options are decoupling and adding lots more mass.

As mentioned, this is because bass can travel further through solid surfaces, which mass effectively prevents.

Hopefully, by trying one or more of the above solutions you should end up with a home effectively soundproofed against bass frequencies.