Two of the enquiries we get here are about noise from outside and one is about noise from inside, and they need opposite answers. This page is mostly about why the outside one is harder, because a town with a highway and a rail line through it generates exactly the kind of sound that insulation is worst at.
Truck and train noise is low frequency
A diesel engine under load, a loaded trailer over a joint in the road, a locomotive at idle a few streets away: the energy in all of those sits low in the spectrum. Low frequency sound has long wavelengths, it passes through light assemblies as if they were not there, and it is reduced mainly by mass and by decoupling, which means heavy layers that are physically separated from each other.
Insulation in a cavity works on a different part of the problem. It absorbs sound energy bouncing inside the cavity and it damps the resonance between the two faces of the wall, which helps meaningfully in the mid and upper range: voices, television, footsteps, a dog. It does comparatively little for the rumble of a truck on the highway.
So if the complaint is the highway, the honest ranking is: the windows first, then mass on the wall or ceiling, then decoupling, then what is in the cavity. We would rather tell you that than take the job and have you still hear the trucks.
Where open-cell foam genuinely earns its place
Inside the house it is a different conversation and foam does well. Open-cell at about R-3.5 to R-3.8 per inch is the acoustic material because it is soft, open and absorbent, and it fills a stud or joist cavity completely with no gaps at the edges to pass sound through. Closed-cell is rigid and dense and is the wrong choice for sound; using it because it has a higher R-value is a mistake we are asked to undo.
The three interior jobs that work are the wall between a bedroom and a living space, the floor under a bonus room over a garage where the garage door and a vehicle are the noise source, and the wall or floor of a basement that is being developed as a separate living area.
The flanking paths nobody accounts for
Sound takes the easiest route, and in a house the easiest route is usually not through the middle of the wall. It is under the door, through the shared cold air return, through the ceiling into the attic and back down on the other side, through the electrical boxes set back to back, and around the edge of a floor where the subfloor runs continuously from one room to the next.
A cavity filled with absorbent material and a door with a two-centimetre gap under it will disappoint every time. The gap under the door is the cheapest item on the list and it is routinely the largest one.
What we will not tell you
We will not tell you a sprayed cavity makes a room quiet. It makes a room quieter, by an amount that depends on what the rest of the assembly is doing, and the honest version of this work starts by naming the frequency and the path rather than the product.
Who you are dealing with
We do soundproofing spray foam insulation Coaldale ourselves. We scope and quote it, we book it, and our own installers spray it -- one company, one point of contact.
Soundproofing Spray Foam Insulation Coaldale: Common Questions
Will foam in the walls stop the highway noise? It will reduce the higher-frequency part of it. The low rumble is a mass and decoupling problem, and the windows are usually the weakest element.
Open-cell or closed-cell for sound? Open-cell. It is the softer, more absorbent material and it fills the cavity completely. Closed-cell is rigid and performs worse acoustically.
What is the cheapest thing that helps? Sealing the gap under the door of the room you want quiet, and the back-to-back electrical boxes in the shared wall. Both are small items and both are usually bigger leaks than the wall itself.
How much does soundproofing spray foam insulation cost in Coaldale? It is priced per board foot over the sprayed area, so a single wall or one floor is a small scope. The cost of making a real difference to outside noise usually sits in the windows and the added mass rather than in the foam, which is worth knowing before you budget.
How do I choose a soundproofing spray foam contractor in Coaldale? Ask them which frequency range they are addressing and what they will not be able to fix. Anybody who promises quiet without asking what the noise is has not started the job.
Size the assembly with the R-value calculator, then get a free Coaldale quote. More on Soundproofing Spray Foam Insulation Alberta province-wide.