Airborne noise is sound that travels through the air. Examples include the sound of a TV from the room next door, people talking, and the incessant barking of a neighbor's dog (our own dogs would never bark incessantly). Airborne sounds travel easiest through the air, and will find even the smallest gaps and cracks to travel through, so it’s essential to build airtight barriers with enough mass to block the sound. In a floor-ceiling assembly, the STC rating is a measure of how well the assembly stops airborne noise.

Impact noise travels through the building’s structure and results from physical impacts, like footsteps. To stop impact noise, we have to isolate parts of that structure to prevent the easy travel of noise. We typically do this with rubber or by creating physical separation. Any contact points are potential highways for the sound energy to travel through. In a floor-ceiling assembly, the IIC rating is a measure of how well the assembly stops impact noise.

For a finished drywall ceiling, you can have either type of noise and poorly constructed floor-ceiling assemblies tend to have issues with both. You might hear the chatter from your upstairs neighbors (airborne noise) as well as the stomping of feet (impact noise). Depending on the type of noise, you have different solutions available to you.

Soundproofing an Existing ceiling for Airborne Noise

When dealing with airborne noise - say the voice of your upstairs neighbor who loves late-night phone call – there are 2 basic considerations.

1. Do I want to tear out the existing ceiling and start over?
   
2. Is the sound is going through the ceiling or is it going around the ceiling (or through gaps)
   

If you want to get the best possible performance, you should remove the ceiling you have and start over. In that instance, we basically always recommend RSIC sound isolation clips. They have a proven track record of performance, and are used in well over 100 UL rated assemblies. The steps we outlined in the “how to” section above covers the basics of this approach.

If you don’t want to remove the existing ceiling, your best option is to add a new layer of 5/8” drywall with Green Glue between your existing ceiling and the new drywall layer. Utilizing Green Glue will give you a substantial boost over just adding a new layer of drywall and is an excellent treatment for airborne noise (not impact noise).

Let’s move onto consideration #2, whether sound is “flanking” around your ceiling. The two most common things we see here is (1) someone has canned lights or some other hole in the ceiling or (2) sound is traveling through the vents that connect the rooms.

If you have canned lights or other penetrations in your ceiling, your best treatment is to seal up around the perimeter of those holes. Even a very small hole will allow sound through it (similar to leaving the door to a room open), so you want to seal EVERYTHING up. Imagine the room is a swimming pool and you don’t want any of the water to leak out

If sound is traveling between rooms through the vents, you should check out our article on HVAC vent soundproofing where we cover your options in detail.

Soundproofing AN EXISTING CEILING for Impact Noise

Let's shift our attention to the impact noise, which almost always accompanies airborne noise – and is often the bigger problem. To stop impact noise, the key is to isolate part of your barrier from the building’s structure so that impact noise can’t pass through. That isolation can occur at the floor or the ceiling, so for impact noise you have two options:

1. Treat the floor of the room above with a rubber underlayment
   
2. Treat your ceiling with sound isolation clips (RSIC-1)
   

Which one you choose will depend on your specific situation, but the good news is that both options are excellent for impact noise AND airborne noise.

For treating the floor above, we go with UnderBlock or UnderBlockHD. Both are high-performing rubber underlayments, but the HD version will get you better IIC and STC ratings. For large multi-family projects, UnderBlockHD is the preferred option (contact us for details!). For anyone budget-concious the regular UnderBlock is an excellent floor soundproofing solution.

For treating the ceiling to stop impact noise, the only option is the RSIC-1 clips. Any recommendation that does not include sound isolation clips will not stop impact noise and should not be pursued. If you have questions on your specific project, reach out to one of our soundproofing experts!

Congratulations! You've just graduated from Second Skin's crash course on soundproofing an existing ceiling. While each project can have a bit of nuance, the core tenets remain the same. We’d recommend checking out some of our solutions, and if you have questions reach out to one of our team members to help get your project kickstarted in the right direction. Soundproofing issues ARE fixable, and we're here to help you achieve your soundproofing goals.