You’ve done a good job of identifying the usual suspects, but I’d skip the front floors.

The front floorboard is really thick and sturdy. I did mine, but came to realize it is probably not a source of noise. I did virtually every inch of my interior, including the halo. That exercise revealed a lot of noise leaks, the floorboard is the least likely.

 

Heck, just doing the back half of mine made it tons quieter.
Might want to just do the back and see if that satisfies you.

 

Here is a good reason not to do the floors.
Overview
[img alt=""]data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAA AAgCAMAAABEpIrGAAAAgVBMVEUAAAAQcP8IZf8IZ/8JZv8HZf8IZv8IZv8IaP8JZ/8HZv8IZv8FZf8YcP9FjP+TvP/g7P/////R4/9Vlf8QYP+Es/9kn/8IZv8nef8JZf8AYP/v9f/Q4v/B2P9GjP8HZv+yz//Q4/83g/8HZv/g6/+Dsv8HZf/n7//////////e6//ZLyHjAAAAK3RSTlMAEGCfz+//XyCQj98w/////////xD//6D/kBD/////7////8///5Cgz+/vONkvXQAAAPJJREFUeAF9kkUCwzAMBGVSGMrM3P//rxBaB+e6s0YREFJpw2y0cgS1cT3DQLmNWPjcwK/XA24RWIuEdg4j7OtHUX0NYedxko5+jCeZMc0En8F sVDDHSd1WDoFdIlogX46awopozWA+ythsd7s9Zxy mJBkcs3wcMZC0YHDKhDNbKLowuGYC21zINIWUbQ7 EwwJT7YogqgTTKaTY4tIp7HDIRadwwzVlKVyv11H G9cekFBxam8FbTInuQ4LCd3cL2Uzd+4UV/VkHfUIgMLRdQuBi7JsCxh5rQEAfrO9NYSWojruwB OOhDoR8PF+j0fuipNX+AmbCIviMIiwCAAAAAElFT kSuQmCC[/img]
[img alt=""]data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAA AAgCAMAAABEpIrGAAAAM1BMVEUAAAD+/v41NTUBAQEAAABZWVknJycWFhaZmZmIiIjp6ellZ WXMzMzX19eurq54eHhHR0dExXFyAAAAAXRSTlMAQ ObYZgAAAPtJREFUeAG8kAWOBDAMA9d1Sin+/7XXbpZZdBaURlMrhx28ycGCD/n0bvkBwJf8C+AoIvRAWGtMyHGtCWkfxW+DRopuuI jUtTQJDStevNoXWaRjRSllLd1O8FFhgEZx2BmkAm HC8HwpOUyxSA50VqOjXgAl50URvNWPBRcAnmwnhb cduthqQCO9KYTFBG7eDWoK1T47AZX9DuiUYT/TuhX3MGpnD51kPprSA9Dl+BCKl7jWHHEHmHsLWhN ZZMxPQCLTEuy+cYF6D9i8Q5e2Lcyz4AGwKdJbX0p 7AegC2qnvxAsAxQRAYH8J6Dg1a/lvpKRJinMW4cxLMPsDAJjSCaG8cPmnAAAAAElFTk SuQmCC[/img]
[img alt=""]data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAA AAgCAMAAABEpIrGAAAAilBMVEVHcEz/RQD/RgD/RQD/RQD/RQD/RAD/RQD/RQD/RQD/RgD/RQD+////PwD/OADr9Pbi6+73/f3K2+P7flzT4ugAAAL5ZTr2+Pj0uKzGy83+ThP70 cb7kXjc19frnY/+6+XajYHxck/Ro6M8LSr/WAAFFxz/bkioNhLTQCNkZWaCUELvGwDeWT6IfHsSwPnoAAAA C3RSTlMAyU9RouIMIvWPUzQQe5EAAAGkSURBVDiN hVPpeqwgDNWpjk5jWARxt9rZu7z/6zVAnWpv/e75g3JOCEkOQfDA/jkKU4A0PDztg3+RREQ+ECW/+QP8wmEdHq9IZAwhXhySpCuedW1rENJkg8cuIzTw o1ifD9e7IMHAAOK/7nc7Hz9FJuWA802Tdfz5ikoL0aP7s0miVf7rEQHN MDZeEFH/PIGuuEa9vamGUZWIXrEPnmxdjVLALtVL5vBSXRgo EhK1sxlYV9Jumy3QkrbsmL1mCKiyDSiEMEiBtVuC lkEawEPw+joT8xcJwAoqXsosG9/N4PeH92mkpeSVFaRUtuZSljcwxgsMmFuZSa7txOi SgJMopfw4nS5eMJ1OHxQhJmpF6BrpkvRKzX1Qqpc +AZX57AbMOUmk6GtCL6SUtNGha5RvdS8EbR0LhyN 9ctF/t9rloAHSBHldFOdzUdRcCK0V+mH5cbMxz3Mt6ntR 3Gti83xk87i9YdhU504jtF1rxRbWdpbDZui1I3Pd D94O8dq0DExXEToDLnxh69mVSJ6xZoENfo34P/zP09v9RUfb784+/93i+X8BtrYxyahtbccAAAAASUVORK5CYII=[/img]C5 Corvette floors are
innovative composite structures, essentially balsa wood sandwiched between fiberglass (SMC), creating a strong, lightweight, and stiff floor that's better than steel for weight savings, stiffness, and noise reduction. This construction uses lightweight balsa wood for core strength, providing excellent rigidity and sound dampening, a key feature in Corvettes from 1997-2004 (C5) and even into the C6 generation.

 

I’m sorry I guess I did something wrong. Just wanted to post the makeup of floors of a C5

 

Yeah, you sure copied that link wrong and then posted it wrong too!
I can't even pick the correct link address out of that to try and fix it for you!

 

The key point of it is still there. At the end of it.

 

Well, one planned upgrade just went to the top of the list, yes, I have one. I was told some improvement can be achieved by changing tires. Had on my list to check DOTdates, but hadn't gotten around to it. All 4 TPSMs are bad, so I went to get them replaced. When my tire guy broke the first bead he called me over. He pushed down on the side wall and you could see cracks in the tread in many areas, dry rot. I said wait and looked at the DOT dates, the car still has the original tires on it. 23 year old tires, not good. I'll know after tomorrow when they come in how much difference the tires make in the noise.
Special wrench for the Wife's Mustang will be in Saturday, 10-minute job and it will back in the garage and I can pull the Vette into my shop to do the window adjustments and begin some sound deadening.

Bad news - on the way back from the tire shop I saw some glare in the road ahead but couldn't tell what it was. Turned out to be 5 or 6 galvanized buckets, did the best I could, but one hit the lower spoiler and broke it, just inboard of the right-side wheel. Rear wheel made it perfectly flat. Looks like spoiler and spoiler frame/mount/brace are now added to the list.

 

Update 12/12/25 13:30 - Just drove back from the tire shop, had a set of Michelin (Pilot Sport All Seasons) tires put on the C5. I've only experienced the drive back, but asphalt, older asphalt, the noise has improved greatly, or should I say the cabin is now bearable. Still plan to follow through with some sound deadening and test after each section is done, to see what improvement it's made. It's a shame that I'm retired, or I could be using a Docimeter to quantify the process. Not a Nerd, however it would be nice to actually quantify the improvements, over the same roads and same speeds, not just feeling like it's better.
Fact the factory 23-year-old tire vs the Michelins is great improvement.

 

I believe there are decibel meter apps for your phone.

 

2 Days of great progress in noise reduction. Yesterday it was the NEW tires and today I adjusted the passenger side window and put sound deadening material on the outer door.
I had previously mentioned it appeared as if someone had put adhesive or sealer on the outer regulator clamps. Well, as a Member mentioned it could be, it was not sealer, but the actual rubber from the clamp adhering to the glass. It took about 10 minutes each and a 0.013 D guitar string to separate the rubber from the glass. Got it aligned and tensioned properly and with the sound deadening I have no indication of noise from that side. I can hear some minor wind noise and roar on the driver side so next week I'll fully adjust the driver side window and install the deadening as well. Test drove it on various surfaces 70 - 95 and you could actually have a conversation.
It's quiet enough now that I can hear the sound from each direction instead of an overall roar. Side note; I installed a new window and lock switch as the original one was brittle and cracked. Small stuff, but it all matters.
Thank for the Info and Suggestions, it's getting there and is much more pleasant to drive.

 

Downloaded one of the many sound meter apps and played with it a little, while going down to get breakfast this morning.
Decibels accelerating moderately was in the 88-90 db range, steady state cruise at 55 mph was 69-70 db, sitting idle in my driveway was 52-53 db.
Not sure what some newer cars do, but seems pretty quiet to me.

 

85db is where hearing protection is recommended. 50s is great, sounds like your's is fairly quiet.

 

Extended exposure at 85 db and up.
I trashed my hearing way back in my teens and twenties, when I thought I was invincible, with too much top fuel and top alcohol starting line time with little protection, bad tinnitus.
I plan to do some better sound tests, get out on the interstate and see what a 70 MPH cruise shows.

 

Much the same without top fuel. Mine was from loud music, to date - 58 years of motorcycle riding and racing, working in a boiler house and machine shop, heavy equipment, welding and grinding, and finally 30+ years of working around high pressure pipelines. Only over the past 20 years have I started wearing the protection I should have worn 50 years ago.15 years ago I found it wasn't the sound from the engines and exhaust of my bikes, but the wind noise, I don't wear helmets unless racing I started wearing ear plugs and covering my ears with a bandana and it was like a completely different world. My tinnitus is constant and the exact pitch as the dishwasher alarm, my wife thinks it's amazing I can't hear it even within 4 or 5 feet. My hearing loss is from 50% - 85% depending on the frequency. Sadly much of the loss is at the same range as my grandchildren's voices, they all know when you talk to PawPaw to look at him, it helps with the projection and I can read lips fairly well. The side effect of that is while I can hear when multiple sounds are filling the room all I here is a roar, to the point I get agitated. I did some study and found that is quite common. I now have several sets of protective earmuffs and boxes of ear plugs in my shop and storage sheds. I even carry plugs when we go to restaurants. That's why it is important for me to get the cabin noise down. As the levels were originally, I couldn't enjoy the car.
Thanks for everyone's help and suggestions. What may not be an issue for some is very important to me.
I now play music at a much lower levels and need my surrounding quieter so I can enjoy life.

 

40 years in aviation!!

 

Completed the Driver side window tension adjustment as well as sound deadening the door. I also installed sound deadening on the area just behind the seats and over the ridge to the cargo compartment.
Can't test drive right now because the driver seat is at the upholstery shop having a scraped panel replaced and restitched, that I'm sure was from the previous owner struggling to get in and out. Tomorrow or Saturday I'll try to get to the rear compartment with deadening and foam mat.

 

My wife has had some medical issues, so I've not been able to drive the Vette or get back for a report. Got 80% of the rear cargo area done and ran out of material. I got the seat back from the upholsterer and he did a great job.
Took it out for a test drive today and all I can say is it's like an entirely different vehicle than the one I drove initially. Up to 55mph is about the same level as 10mph, and from there to 80 isn't that much louder. I could easily hold a conversation if I chose at 75 or 80. The tires seemed to make the most difference, then the sound deadening (especially the doors), then the window adjustments. Now it's quiet enough I can detect some wind noise that I can't pinpoint the location (possibly the roof).
Bottom line - I've gone from wanting to turn it to thinking it's going to be very enjoyable.
Thanks for all the input and tips.

I mentioned I had hit a bucket. I was able to removes the right-side spoiler (air dam) and straighten out the sheet metal frame and put it back on. Can't tell it was ever damaged.

 

Sounds like a successful project 👍

Truly amazing how much quieter these can be with some thoughtful changes.