Hey guys, I have an 05 Camry company car previously used by another person. So what I noticed was that when I closed the boot lid, it sounded very metallic and hollow like closing a standard Viva door with its hollow metallic sound. Since it's a company car, I'm not going to spend loads of my money on a car which isn't mine. So I took this opportunity to try out some DIY acoustic damping to dampen the metalic banging sound when you close the boot lid.
So I went to the the hardware store and bought some weather seal bitumen with alu foil roll. The size was the standard 2"x10m. Cost RM13 after discount.
Firstly I opened up the clips holding the insulation molding.
Once removed you will be able to see the ribs and the sheet metal. Upon inspection I found that the ribs was not attached to the sheet metal like normal. It seems like all the glue has detached from the sheet metal which makes the metallic bang even worse when closing the boot not to mention added vibration and sound when driving the car and sound reverberating off the loose sheet metal.
So started to cut the bitumen strips and started sticking then to the sheet metal and ribs. I decided not to stick the strips all the same direction as to help not to create the same harmonics so with each strip at a different length and direction. I hope to not have the sheet metal have the same resonant freq so different spots will resonate differently helping to reduce any resonant sound which might occur.
After some research and much reading, I have found that fully damping the metal also doesn't really help much more and it just adds extra weight. You have to get the right balance and position. Basically if you tap the sheet metal and that part still "rings and echos" you need to dampen that area. So from what I have read about 70-80% coverage is more than enough. If you over dampen the panel, you will add weight and the car will start to feel "pressurized and enclosed" what you want to get is an "airy quietness" which is less stressful. (But this is very personal, but some would like it the other way round which is fine).
Once finished I put back the insulation molding and all clips and tested the boot by closing it and it sounds just right. Nice thud but yet still light. Then I took it out for a test drive and it was quite noticeable that the back was quieter and the road noise started to shift slightly forward.
Then I went back home and had some extra bitumen tape left. So I decided to open up the side right and left insulation moldings to expose the rear side boot panels. I saw that the factory has already factory stuck a damping panel right in the middle of the whole panel. So with what I had left, I started to tap the side panel where the metal sounded hollow and ringing. So that was the place where I stuck the bitumen tape. It was basically in the lower half section of the panel. The upper portion sounded ok as the upper portion started to curve and was quite solid and didn't flex. The lower portion was more flat and flexible which needed some damping. So I had just enough to do both sides, with that I finished up. There was some places which still could have done with more damping but will leave that for next time when I get some more. So after installing everything back I went out to for another test drive and it was even more quite at the rear. The tyre noise started to move further up closer towards the rear back seat (bench). I guess that is where the fuel pump and tyre wheel arches are and there usually is little damping there. So that was the end of that short test.
So what I learn was how to properly place the bitument tape and it is accurate to say that you should not over damp the metal. I'm more than happy with just RM13 spent. Will start to buy more to do the door and the floor next. The good thing about doing the Camry is that the car already has sufficient soft type of sound absorption material which helps alot so you don't need to stick stuff like Superlon insulation which helps to save money as well. I think when you start to do that you might get very close to over damping the Camry. I also checked the rear deck board where the speakers hang, its also pretty well damped from the factory so no real work needed there as well. But Could do with alittle to plug up some holes and little tape here and there on the back board.
