Sound Proofing
 

Here are some numbers before and after adding sound dampaning material. We did not add any material to the front foot well. Almost four layers were added to all the flat areas in the rear and one to two on all curved areas. The materials used were butal rubber and vinyl foam.

Before at rear view mirror 91.5, foot wells 94.8, door 93.2 and the rear 98.75.

After at rear view mirror 88.7, foot wells 91.35, door 88.6, rear 89.0.

The doors on the before reading were already treated when the speakers were installed. I think the decrease was from the rear noise not echoing through the car. I can tell a big difference and so can everyone I talk to on the bluetooth.

The added weight is noticable when driving the car. Personnally I think it drives better. To me the rear seemed light at high speeds, it has now settled done a little.

These numbers are from a Nismo. I do not know if the other models have any added noise reduction from factory.

Troy

Thanks for the numbers. I recently applied Dynamat to the doors and hatch area and found it made a real improvement. Your numbers seem to confirm my impression of the improvement. I am planning on working on the foot wells next.

I've always thought a db meter would be a nice addition to the tool box, which one did you use and was it pricey?

I am not sure what name brand the meter was. It was a digital meter. The shop I had do the work had a meter so we took the car out before and after. I was driving and witnessed the numbers.

Troy

Subjectively, how much of an improvement was there?

When I did my car the guy said footwell has good stock insulation so not needed, but I wasnt there so havent seen my car opening up

Subjectively it was a remarkable difference. Before the sound proofing people had a problem hearing me on my bluetooth at 60+MPH. Now no one hears any "wind noise" when I am talking to them. It got rid of a lot of the road noise. The tire noise is still there. You can now hear the pinging of the tires when you hit rough cracks in the road, but not very much true road noise. I also agree with the previous post. I was told there is a lot of padding in the front wells. I still might do it just to see. As you can tell from the data collected a lot of the noise is still coming from that area.

Troy

Thanks for the Stats...I recently Dynamatted my Z and it really does make a difference in the feel of the car, reduction is road vibration and an improvement for hearing the audio.....What I now hear is that great sound from the motor..Which is what this car is all about !

This thread has been dead for some time but I just wanted to suggest using a smart phone sound meter ap rather than buying a dedicated tool. There are many of them, many are free and they work great. I have SPL on my Droid razr

Sound meter apps are available for most smart phones.

I would like to know how much weight this "sound proofing" adds to the vehicle?

IIRC, the 10 sqft sample from DTMat was about 4 pounds. Covered most of the rear area. Twice that would probably finish the rear and do the doors.

I installed some of this 3M Sound Deadening Pad on the wheel wells. It's self adhesive and it works well. I lifted the car, removed the rear wheels, cleaned the wheel wells with soap and water, let it dry and went at it. Where I could install full sheets I did and were I couldn't I cut pieces to fit almost like a jigsaw puzzle. It completely eliminated the dinging rock/stone sounds inside the cabin and made it overall quieter. I drove around yesterday in the heat of the day and the hot highway and the hot exhaust/brakes didn't affect it, the pads stayed on. I used 6 sheets and had about half of one left, the material is very malleable and heavy too; the 6 sheets weighed in at 30 lbs. I haven't driven in the rain so I don't know how it'll do once it gets wet but the adhesive is very good. I think it took about 3 hours to do both rear wheel wells. Lots of work! I did this to eliminate the rock/stone dinging sounds back there, you still have the regular road noise which comes in through the spare tire and hatch area behind the seats but no more rock noises.

Good Job! Damn I hate rock noise.
So Benibiker, you used 6 sheets, you ordered 6 sets at 14.64 each from Amazon?

Impressive numbers considering that a difference in 3db is basically 33%. I have extensive amounts of sound deadener in my car as well, but wasn't wise enough to check the before and after numbers.

We wont get into how much sound damping I put in my car...lol