What are the major sources of cabin noise in cars?
June 6, 2013 1:46 PM   Subscribe

I've been thinking of buying noise dampening products to make my car interior quieter. It seems that the common approaches are to get spray-on dampener for the wheel wells and peel/stick sheets for areas like the trunk. Some people go nuts and tear the entire car apart to line the entire cabin with sheets. I don't have time or money to go nuts, but I would be willing to be a little crazy to target the top 3 or 4 sources of cabin noise, if I could figure out what they are.

My guess is that the list would look something like this, but I'm hoping someone can point me to some actual research on this.

1. Engine vibrations coming from everywhere
2. Wind noise coming in everywhere (especially doors?)
3. Tires on the road noise coming through wheel well
4. Transmission noise coming through floorboard
5. Road noise from trunk and floorboards

If I knew for sure that one area is a major culprit, I'd totally be willing to (e.g.) disassemble a door and dampen the inside, but I'm not going to go through that effort on a guess or just go nuts and dampen everything.
posted by brenton to Travel & Transportation (5 answers total) 3 users marked this as a favorite
Depending on the shape of the vehicle, there can be a number of problem areas. Generally, the doors are biggest culprit.

As you said, something like Dynamat or Raamat, coupled with ensolite or other insulation can yield big results. It doesn't take much to be effective - some people will do 2-3 complete layers, but that is totally overkill. You can get a 80-90% improvement by just adding some mass to the panels.

What I did on my truck (an Access cab Tacoma) was do the doors and the back wall first. Then the floor came after. I did the ceiling last, since I had to drop the headliner to install some antennas anyway - I probably wouldn't have bothered otherwise, and I had excess from the other parts to use. All told, it was only a a few hours work, and is a big improvement in ride comfort.

That said, you can only get so far - the windows can't be insulated at all, and no matter how much dampening you put in, hollow doors and panels will resonate. And anyway, the silence only makes interior rattles that much more noticeable.
posted by Pogo_Fuzzybutt at 1:56 PM on June 6, 2013

You're missing a major one here, and i realized this after driving/owning 3 "generations" of cars either on my own or via a family member.

1. a 1966 plymouth, which is basically a metal cage with vinyl glued on the inside(even the dashboard is sheet metal! so are most of the doors!)
2. a 1985 toyota, which was a mix between the above and plastic.. but with no real solid "interior" to separate you from the outside much, still
3. a 1999 subaru, which is essentially the same as the subarus they sell today.

One constant between all the cars is road noise that works sort of like those bone conductive hearing aids/headsets. The road noise travels up through the suspension, especially the pivot, and not sprung end of it where it's fairly solidly mounted to the frame or subframe and then that vibration is just transmitted and resonated through the entire structure of the car. If you put your hand on say the door pillar while you're going 65mph you'll feel this vibration.

The new cars have less wind/engine/transmission and exterior noise, but it seems like for the most part this deep resonant tires-on-road vibration being transmitted through isn't killed by anything less than SERIOUS engineering in say, a $55,000 mercedes.

You could fill every gap in the car with expanding foam and not kill this noise. My 1966 car is just as loud and quiet at 40mph as the subaru, or even my girlfriends newer nissan. It's not until you step up to serious luxury cars that you start slaying that type of dull roar noise.

Basically any new car now seems to be about the same unless it's like, something actually crap like an aveo too.

So what i'm saying is i think you might be able to mitigate the entire general noise by like 20%, but overall you're not going to make a huge difference you'll really be happy with unless you're getting tons of wind noise from bad window seals or something.
posted by emptythought at 2:01 PM on June 6, 2013 [1 favorite]

Tires, especially if they get irregularly worn. Kills me every time.
posted by Rock Steady at 2:02 PM on June 6, 2013 [3 favorites]

Wheelwells. Trunk. Firewall.

Doors can be. Newer cars seem to have double seals now, and that makes difference. If you don't have that, you can probably get something like EPDM rubber to make a sort of double seal.
posted by gjc at 2:13 PM on June 6, 2013

Tires. As in, fresh, properly inflated tires engineered for less road noise (i.e. not high performance).
posted by Cool Papa Bell at 6:16 PM on June 6, 2013

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