68corvette

CT200H is not a noisy car, especially at the city.
But as there is not much engine noise, the tire noise sounds annoying.
To improve the situation I thought to try to add some deadening.

At past I have had good experience adding noise deadener (rust preventer) insideof the fenders, so I thought to start from that.
Before the change I wanted to make some type of noise level meaurements.
I did not have good DB meter, so I ownloaded Bosch mobile app, just to get some reference numbers.
It looks like the app reads a bit high, but should be still valid to compare changes.

This is the initial measurement with summer tires, driving 80km/h speed on a highway.
Air fan and stereo were shut down to exclude any external sound sources, though I did not see measurable differense in sound level.

That looks about 80DB

Then I added sound deadener into all fenders, at this point inner fender was removed, I had washed the surfaces and they were dry.
I used 3 days in process. One for disassembly, washing and waiting for drying, next for adding the mass and waiting for drying and 3rd for assembly.
Effort is not 3-days, but there is a lot of waiting.
This is from the back fender.



Then for a test drive and DB measurement (after letting it dtry for a day and re-assembling the inner fenders.

This is probaly slightly under 75DB so roughly 2x less dring noise.
I used the same tire pressure, same road, same speed, etc. trying to keep the conditions the same.

Okay.. then I thought to add some deadener to the trunk.
So I removed the panels and battery.. sounds easy enough =)
And then added sound deadener mats to straight surfaces.
This took one day to do.





Then after assembly againg for measurement.

Maby 73db?
I could not really tell the difference..

Then I added deadener to the doors and swapped the speakers at the same time.
Again I added deadener matt to all straight surfaces where I could reach and then soft deadener on top of water insulation plastic to block some noise passing.




And again to check the difference..

The scale was different in previous measurement, so it was easier to check. probably some update changed it.
But anyways, no measurable difference.
On the road I think I can hear the difference when cars are passing, so noise coming from the side is probably more silent, but does not affect much the cars own tire noise.

I still have the front floor to be deadened, I already added some deadening under back seat, but have not measured the DB.
Probably the thick back seat was already deadening the noise.

Outcome so far is like with my previous experiences that adding something to the fenders gives the biggest effect.

Hope you get something out of this =)

E46CT

Glad you're honest about no measureable difference. Most guys will claim a difference after all that work is done.

The door panel mats will help with a more solid feeling door (and quieter door) as you shut the doors. But will likely do little to nothing for actual high frequency noise (such as you might encounter on the road)

For 2014, Lexus engineers made 94 changes for noise vibration and harshness, including additional spot welds and structural adhesives. They basically made the chassis more rigid as to quell resonance. And probably added some rubberized sheeting (or more of it) to areas deemed necessary by computers. Maybe you can adopt some of the changes (short of the chassis stuff of course) to see if you can get the car quieter. I don't know for sure what all 94 changes are.

Lexus also did this for the NX facelift. They made 100 changes to make the car quieter.