Road noise and how to reduce it

[Kern Dog]

One of the stark differences in older cars and newer ones is the amount of noise that is heard while driving at freeway speeds.
I can go for a ride in a newer Challenger and feel somewhat isolated from the outside world.
The same road and duration in my '70 Charger and I feel overstimulated, almost like you feel after leaving a live musical event.
It isn't all bad but I wonder what can be done to take the edge off just a bit.
Several factors add to the noise so I think that there are areas to address to limit some of the noises that we don't want. For me, part of the problem is that due to some hearing deficiencies, I may have a hard time identifying what is causing the noise that I want to scale back.
I don't want a silent car. Hell no......
I just want to scale it back a little. I just need help finding out what is responsible for the noise that bothers me the most.
First off, I have NO drone. This car has somehow never had a problem with overheating or exhaust drone noise. Somehow, I dodged those two bullets.
Secondly, I have tires that are sticky and wide. 100 treadwear tires do not last long and are not great for wet weather.

How much of the noise that we have is from the wind itself? Looking at new cars, you see hidden rain gutters, flush bumpers, wheels pushed to the edges of the body and mirrors with rounded or pointy shaped sections facing forward. For contrast, look at this:

Starting from the rear, you have a bumper that has a noticeable gap from the body where air can get disturbed when flowing by.

Moving forward, there is the rear wheel opening that has a gap between the tire and body. Above that there is the quarter window taper which has a bit of a pocket in it at the bottom. The side view mirror is almost flat at the front side. Above that, the A pillar has the start of the rain gutter and the wing window. The windshield wipers certainly grab the air along with the front wheel openings but how about the huge sugar scoop grille?

Looking at a late model, you can see a lot of differences if you look close.

As you might expect, the recessed grille is a step backward for aerodynamics but was deemed necessary to get the styling right for this car. Still, look at the gentle shape of the front bumper, not how the tires are out to the edges. The windshield wipers are tucked down and out of the air flow. The mirrors have no flat or blunt faces either.

Part of what attracts me to the classic cars is the styling. I'm sure that you feel the same way. Because of this, we are limited as to what we can do in terms of styling changes to reduce the noise. I do have my tires out wide but not for aero...It is because I loved the NASCAR look:

I need windshield wipers. I love the way the grille looks. I may change to the late 1970 style racing mirrors though that alone will result in almost no noise reduction.
What else can be done to reduce noise?

In 2012, I did add a fair amount of "Rattle Trap" matting.

The late models have flush mounted windshields. This can be replicated but now I'm looking at a custom windshield or shrinking the stock opening and fitting the stock windshield, both options are not cheap.

Flush door handles? Hmm...Hard to do without going custom....plus, I like the stock design.

 

[RemCharger]

Convertible a pillar moldings. ( 500, daytona)

 

[Kern Dog]

I am just guessing but I think that the noise comes from several places and just blend together to make what equates to a noise salad.
Wind.
Vibration.
Engine-transmission-exhaust system-wheel bearings-brake pads-tires.
Road surfaces.
I have noticed that the Challenger is noticeably quieter with the windows up. The Charger is only mildly quieter then.
I have frame connectors and torque boxes, HD suspension and Bilstein shocks so there isn't much flexing going on.
However....
I'm running a solid lifter cam, 2" headers, 3" exhaust and a manual transmission.
How much of the noise I'm experiencing is coming from valvetrain noise? I can stand in front of the car with the hood open and hear the lifters and rocker arms clicking away when other engines with hydraulic cams just hum along nicely. Bump that up to 2200 rpms at 70 mph and how noisy is that?
I need to take the car out on the road and shut it down at 70 mph and see how much of a difference I notice. I suspect that 80 % of the noise is the engine.
I don't have a lot of exhaust noise from the mufflers. These Ultra Flo mufflers are quieter than the Flowmasters I had before. In fact, I've thought of reducing the engine noise while increasing the exhaust noise...if that makes sense to you. I'd rather hear the exhaust than the solid lifter clatter.

 

[R413]

Get up some speed on the freeway, **** to N and turn the engine off, how is the road noise now?

Fond a NEW paved asphalt freeway and drive on it, turn the engine off, compare this to a concrete or old pavement.

 

[Llamaback]

Interesting post. It seems like a big contributor is how much higher the front end of the charger sits than the challenger. The front bumper of the challenger looks like it would have far less air traveling underneath the car, or air that is not hitting major engine and suspension components. Stock mopar LCAs and the front edge of the k frame would create a lot of wind noise! I daily drive a 70 Pontiac Tempest as much as I can and it has really started to bother me how windy days on the highway affect me so much more in the Tempest than my modern car. I feel like a sail in the wind in my Tempest compared to my Mazda.

 

[Tony Tee]

It gets quiter as your age and hearing loss increases! LOL!

 

[RemCharger]

Properly adjusted windows and tight seals go a long way.

 

[Kern Dog]

Get up some speed on the freeway, **** to N and turn the engine off, how is the road noise now?

Find a NEW paved asphalt freeway and drive on it, turn the engine off, compare this to a concrete or old pavement.

I do notice a slight difference in noise depending on the road surface but not like I notice in my truck and the Challenger. The Charger has road race type tires with no sipes or rain drainage grooves.

The tires on the truck have those small grooves.

I don't think much noise comes from my tires.

 

[fine69]

I say embrace the overstimulation of your charger rides. It’s just part of the muscle car experience.
My car has terrible wind noise on the highway but Iʼm sure with new properly fitted seals and weather stripping it would be just fine.
You can compare it with new cars all you want but at the end of the day…..it ain’t a new car!

 

[Ron H]

You’ve pointed out a ton of things that can contribute to unwanted noise. I did lots of sound deadening on my car including the doors, ¼ panels, rockers. Not sure what I was thinking since it’s a vert, lol. But thought it might limit some road noise. Seems to have helped with floor heat from the exhaust.

In my encounters with noise, it’s been the dang TIRES making a difference. One thing I want is a quiet tire; but didn’t look for this with the set I have on my old ride now. And I changed from Flowmaster 50’s to the Hemi mufflers that quieted things some at higher speeds. They mellow some at high rpm's.

 

[F4R/T]

Tires can really change things you may try a set for kicks..

 

[R413]

When you shut off the engine at freeway speeds, what changes, and what stays the same?

Same:
Tires on the pavement
Wind over and under the body
Rear axle And driveshaft spinning, but zero load.
Wheel bearings

Changes:
No engine noise
Reduced or altered transmission noise
No exhaust noise.

So if it changes much or gets rid of the undesirable noise then you know where to look.

 

[Bighouse]

The new challenger is also filled with expanding foam everywhere.

 

[1967coronet]

Late model cars also now have acustic glass to reduce road noise.
Insulation on the engine side of the firewall, under hood mat, fiber glass rolls in the fender tops , insulation at the rear of the fender from the top to the rocker.
Plus like bighouse posted spray foam/ sound insulation is in every nook , qts, doors , dog legs , you name it.
Trunks are all fiber matted, top , bottom sides.
Many have fiber matting between the metal exhaust shields and floor pans.
Slope of the glass , plus all the other things kerndog listed.

 

[Kern Dog]

When you shut off the engine at freeway speeds, what changes, and what stays the same?

Same:
Tires on the pavement
Wind over and under the body
Rear axle And driveshaft spinning, but zero load.
Wheel bearings

Changes:
No engine noise
Reduced or altered transmission noise
No exhaust noise.

So if it changes much or gets rid of the undesirable noise then you know where to look.

This is exactly my point.
I suspect that a large part of it is the engine and exhaust system. A milder hydraulic cam would certainly be quieter.

 

[ckessel]

I never realized just how much noise tires make on a freeway, not truck mudders etc, but passenger car. I was driving the Audi TT convertible my honey had in 07, top down on the 10 heading to Vegas, it was mind boggling how loud they are at speed. Not our car but others, as annoying as fingernails on a chalkboard, pulled over and put the top up, problem solved. When I was working at the ranch in Fallbrook, 08 to 10, I could hear the tire noise from the 15 freeway which was almost 10 miles away and had several hills in the way. It was a constant background noise, no definition just a white background noise.

 

[Kern Dog]

I agree. There can be a variety of tones associated with tires.
I have a 55 mph road at the back of our place and at different times of the day and night, I can pick out several different sounds.
Some have a hiss. It sounds like you're spraying water through a hose or a radiator is boiling over.
There is a roar where the tires are off road type with large open spaces between the tread blocks.
White noise is a good description for some too. Just like a low hum, maybe similar to radio static without the sharp tones.
So many cars and trucks passing through are making more noise from their tires than the engine or exhaust. Motorcycles are distinctive, the Japanese ones are very different from the blat-blat-blat-blat of the Harley/Davidsons.
I have a busy day planned but I do hope to get the car out to check. I still suspect that the camshaft and valvetrain are a large part of it. I don't recall the 318 being nearly as loud when I first bought the car. I drove this car 130 miles a day for about a month in April 2000 when I was rebuilding the engine in my Chevy. I had a 2 watt AM radio then and could hear it when driving on the freeway!

 

[themechanic]

A symphony of sound.

 

[Kern Dog]

A cacophony of clatter!

 

[Kern Dog]

A short time ago as I was working on Dwayne's Plymouth....

I was reminded of the noise that is generated by the engine fan....

In his car, the 7 blade fan made less noise than the 6 blade. A few factors are at play though. The shape of the blades, the angle of them and the spacing between the blades all affect the noise. The Mopar 7 blade unit is excellent at pulling in air without making too much noise. I have one in the red car and put one in Dwayne's car.
The Tremec 5 speed manual is quieter running than a few Mopar 833s that I've driven. I do get some vibration but no whine.
I don't notice any axle whine. The rear wheel bearings are the infamous non adjustable type. They are not growling.
In 2022, I did adjust the vent window frame on the left side. That did eliminate a whistle I was getting from that side.