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Impact Noise vs. Airborne Noise
Author: Eric Zuck
Last Updated: February 9, 2024
Read Time: 7 Minutes
Impact Noise vs. Airborne Noise
Author:
Eric Zuck
Last Updated:
February 9, 2024
Read Time:
7 Minutes
Author: Eric Zuck
Updated: Feb. 9, 2024
Read Time: 7 Minutes
In soundproofing, we deal with two main types of sound: airborne and impact noise. Most people really don’t understand sound at all – much less the difference between sound traveling through the air and sound traveling through a structure. We’re not going to get into the whole “sound is an energy wave” thing here. That’s another article. What we will do is hit the key differences between impact noise and airborne noise and how they require very different soundproofing treatments.
Ready to dive in? Let’s get straight to it and discuss the difference between airborne and impact noise and how to soundproof for each.
In soundproofing, we deal with two main types of sound: airborne and impact noise. Most people really don’t understand sound at all – much less the difference between sound traveling through the air and sound traveling through a structure. We’re not going to get into the whole “sound is an energy wave” thing here. That’s another article. What we will do is hit the key differences between impact noise and airborne noise and how they require very different soundproofing treatments.
Ready to dive in? Let’s get straight to it and discuss the difference between airborne and impact noise and how to soundproof for each.
What is Impact Noise?
Impact noise occurs when one object makes direct contact with another, causing vibrational energy. The vibrations then cause sound waves to form. Common examples of impact noise are footsteps on the floor above, knocking on a door, bouncing a ball on the ground, and a washing machine vibrating against a wall. Impact noise, also known as structural noise, can travel through the structure of a building, car, or piece of machinery before re-radiating into the air where it’s then perceived by our ears.
Soundproofing Materials for impact Noise
To soundproof for impact noise, you want to isolate the two objects from each other or damp the system in some way to reduce the ability for the energy to travel through the structure. Think about it this way. If you drop a coin on a metal surface, there will be a loud clinking sound as the coin lands. But if you place a piece of rubber on top of the metal surface, the sound of the coin will be a dull thud.
Ceiling and Wall Impact Noise: Sound Isolation Clips
Sound isolation clips are the best way to stop impact noise from traveling through walls. These clips decouple the studs from the drywall, so the vibrations will not pass from the structure into the drywall. We prefer to use the RSIC-1 clip, because it’s the best option out there. The clips are installed directly to the studs, 25 gauge hat channel is snapped in, and then the drywall is installed on the hat channel.
We prefer clips over the most common solution to isolate the clips: resilient channel. There are a bunch of reasons for this, which we review in our article on resilient channel vs sound isolation clips. The short version though is that there are lots of way to mess up resilient channel, and the performance is not as good as the RSIC-1 clip.
Impact Noise Through a Floor: Rubber Floor Underlayment
One of the most common cases of impact noise we deal with is footfall noise traveling through the floor into rooms on the bottom floor of a home. Floor impact noise is especially an issue with hardwood or tile floors, so multi-family construction often chooses to place a rubber underlayment between the concrete and finished flooring to decouple the floor-ceiling assembly. Doing so will greatly reduce the amount of impact noise traveling through to the lower floor. Rubber underlayment also works great in wood frame applications, and can be used in both residential and commercial applications.
Carpet is also a good alternative to hardwood or tile floors, as the surface is much softer and produces minimal footfall noise.
What is Airborne Noise?
Airborne noise is any type of sound that travels through the air. People talking, music playing, and dogs barking are all examples of airborne noise. Airborne noise travels like water, flowing toward any weak point, like cracks and gaps, and only stopping at dense, airtight barriers.
How to Soundproof for Airborne Noise
To soundproof for airborne noise, you must ensure the barrier is dense and has an airtight seal. You also need to use an appropriate soundproofing assembly.
Imagine trying to have a conversation with one person behind a curtain and one person behind a concrete wall. You will definitely be more successful in communicating with the person behind the curtain because the concrete wall is much denser and more effective at blocking sound.
Take that same concrete wall and drill a large hole in it. Now you will easily be able to have a conversation because there is a large penetration for the airborne noise to travel through.
There are a wide variety of high performing soundproofing assemblies available. The best option for you typically comes down to how high of an STC rating you need to achieve, your design constraints, and your budget.
1. RSIC-1 Clips to Stop Airborne Noise
Part of the reason we love the RSIC-1 sound isolation clip is that it also is excellent for STC. Even a basic wall assembly using 5/8” drywall and RSIC-1 clips on one side will be STC 56 or so. It’s the best performing option for both airborne and impact noise.
2. Use Mass Loaded Vinyl to Add Density to a Wall
Mass loaded vinyl is a popular product used in soundproofing because of its density and ease of install. Installing mass loaded vinyl to the studs before attaching your drywall is a great way to soundproof your wall, and will get you around an STC 50 in most constructions.
3. Use 2 Layers Of ⅝” Thick Drywall to Block Airborne Noise
Always use ⅝” thick drywall for soundproofing purposes. Using ½” drywall is just giving away easy noise reduction. Adding a second layer of 5/8” drywall to one side of a basic 2x4 wall assembly will increase the STC by 3 points or so. Both sides will give you another 3 STC points. When adding additional drywall, we always recommend using Green Glue between the 2 sheets of ⅝” thick drywall, because instead of getting 3 points of STC, you’ll get 10-15. A one sided Green Glue assembly will get you to around an STC 50 in most constructions as well.
4. Use Acoustical Sealant To Close Up Any Gaps
Always use acoustical sealant around the perimeter of your walls, ceiling, and floor, as well as around electrical outlets, light switches, and any other penetrations to prevent airborne noise from flowing through.
How to Tell What Kind Of Sound You are Dealing With
This is going to sound really obvious, but we had to include it. An easy way to tell if you are dealing with impact or airborne noise is to physically feel the surface. If you can physically feel the vibrational energy when touching the surface, there is at least some noise traveling through the structure (impact noise).
If you aren’t sure about the noise in your situation, please reach out to a Second Skin expert for some free help or see more on the basics of soundproofing here.