Suspension Noise Sound Deadening - Low Frequencies over bumps (1 Viewer)

[Kirbster919]

Hey Folks (and specifically folks who have installed sound deadening!),

I have a 98 LX470 and I'm looking to sound-deaden it with a specific objective in mind. The LX has lots of low frequency noise when driving over bumps and other road imperfections. This issue isn't specific to the LX - this is almost every long-roof vehicle and many cars too. I've got some ear issues and this low frequency noise is pretty uncomfortable. I am not sure if these are only from the suspension or if they are combination of suspension noises plus other metal or body parts flexing as the suspension works.

Will installing sound-deading substantially reduce these low-frequency noises? While dampening all noise is probably a good thing, I'm less concerned with the mids and the highs that you hear when driving on smooth roads. I am considering adding noise insulation but it'll only be worthwhile to me if the low frequencies are reduced.

Thanks for your help with this! I've read dozens of posts about sound deadening but wasn't able to find anything about which frequencies were reduced.

 

[brownfox]

I’m not much help, but I’m curious if you have the famous frame weight under the truck. I read a thread about a guy who wanted to get rid of the booming exhaust sound at idle in drive with the brake held. He added the weight and it fixed it.

Mostly people post to ask what the weight is.

 

[Kirbster919]

I will take a look under mine sometime soon. There is a little bit of that 'exhaust boom' at idle with my LX, which isn't pleasant but it isn't too bad compared to some other trucks and vans out there.

 

[nukegoat]

Deadening is usually to reduce resonance in panels. Like imagine a tuning fork wrapped in bacon. It'll still go ding but it won't go diiiiiiiiiiiiiiiiiiiiiing

The rear axle going over obstacles is loud like a truck because it's a lot of unsprung weight wiggling around. I doubt you'll fix it easily.

 

[hickuptruck]

I believe I am well suited to answer your question. My 2002 LX is sound deadened with 2mm butyl sheets. I did doors skins, and the entire floor. You need about 50 sq ft.

Does it help? Marginally. Like barely. I regret spending all that time ripping the interior apart to get like almost non-audible sound difference. Theres less noise from cars passing, and thats about it. My passengers didn't notice and they ride about once a week in it, when I said I covered the car in sound deadening they said couldnt hear any difference. I wouldn't do it again. Does it help with noises going over bumps - not a single bit.

Your suspension noises going over bumps is NVH. NVH was very low when your LX was new. However 21 years later, all the rubber bits have deteriorated and no amount of sound deadening in the body will help that. You need all new bushings and rubber for every bit, and if you want quiet, don't even think about going with poly bushings.

Here are the rubber bits on a 100 series and the number of pieces:
Control arm bushings - You're looking at about 18-20 bushes for front and rear
Shock bushings - about 8 of them
Engine mount - 2
Trans mount - 1
Body mount - 6
Exhaust isolators - 3 or so I think?
Muffler isolater - 1
Steering rack bushings - 3
Differential bushings - 4
Sway bar - about 8 or so bushes.

If you're not doing your own labor, then the cost to get the NVH back to factory spec near off the showroom floor is going to cost you lots of $$$, easily costing more than your LX is worth.

 

[nukegoat]

I believe I am well suited to answer your question. My 2002 LX is sound deadened with 2mm butyl sheets. I did doors skins, and the entire floor. You need about 50 sq ft.

Does it help? Marginally. Like barely. I regret spending all that time ripping the interior apart to get like almost non-audible sound difference. Theres less noise from cars passing, and thats about it. My passengers didn't notice and they ride about once a week in it, when I said I covered the car in sound deadening they said couldnt hear any difference. I wouldn't do it again. Does it help with noises going over bumps - not a single bit.

Your suspension noises going over bumps is NVH. NVH was very low when your LX was new. However 21 years later, all the rubber bits have deteriorated and no amount of sound deadening in the body will help that. You need all new bushings and rubber for every bit, and if you want quiet, don't even think about going with poly bushings.

Here are the rubber bits on a 100 series and the number of pieces:
Control arm bushings - You're looking at about 18-20 bushes for front and rear
Shock bushings - about 8 of them
Engine mount - 2
Trans mount - 1
Body mount - 6
Exhaust isolators - 3 or so I think?
Muffler isolater - 1
Steering rack bushings - 3
Differential bushings - 4
Sway bar - about 8 or so bushes.

If you're not doing your own labor, then the cost to get the NVH back to factory spec near off the showroom floor is going to cost you lots of $$$, easily costing more than your LX is worth.

Well put. And candid. A+++ post. I put probably 300lbs of deadening in a Ford ranger when I was younger. Unsurprisingly it did not help and just made it smell like tar

 

[hickuptruck]

Well put. And candid. A+++ post. I put probably 300lbs of deadening in a Ford ranger when I was younger. Unsurprisingly it did not help and just made it smell like tar

Some days, with the amount of time and $ I've put into my 02 LX, I wish that I would've just bought a used Hyundai Equus or K900, or LS460 as I am really anal about NVH. Sure the LX is decent for other 2002 vehicles out there on the road in 2019, but .....I could be in something better for the same $ I've put, but it wouldn't get me out of the city and into some serene remote places.

 

[nukegoat]

Some days, with the amount of time and $ I've put into my 02 LX, I wish that I would've just bought a used Hyundai Equus or K900, or LS460 as I am really anal about NVH. Sure the LX is decent for other 2002 vehicles out there on the road in 2019, but .....I could be in something better for the same $ I've put, but it wouldn't get me out of the city and into some serene remote places.

Agreed there. And there's nowhere quieter than the middle of nowhere

 

[Kirbster919]

Thanks for the input! This probably saved me a ton of time and effort. I don't think I'm going to worry about sound insulating the LX.

 

[01138lex]

I’ve sound deadened my entire truck in 4mm of dynamat extreme. The doors and rear quarters are double lined, the headliner and floor is single lined.
Single handed the best mod I’ve done on the truck.
Road noise and the door thudd when closed sounds a little nicer but not as nice as a merc.

Cost vs benefits is pretty low, but for some the quietness is worth it. I enjoy driving around with the music off.

I think we logged 16.5hrs of labour at Lexus service centre. :/

 

[Formulaonehd]

I’ve sound deadened my entire truck in 4mm of dynamat extreme. The doors and rear quarters are double lined, the headliner and floor is single lined.
Single handed the best mod I’ve done on the truck.
Road noise and the door thudd when closed sounds a little nicer but not as nice as a merc.

Cost vs benefits is pretty low, but for some the quietness is worth it. I enjoy driving around with the music off.

I think we logged 16.5hrs of labour at Lexus service centre. :/

AN expensive undertaking owch! haha but if your happy your happy. Sounds like 4mm is the key

 

[Kirbster919]

I keep coming back to this. The more research I do, the more it sounds like there are really three things that need to be done. First is the anti-vibration material (Dynamat or similar), then some type of isolating barrier - typically a closed cell foam - and then a sound blocking layer, typically Mass Loaded Vinyl. Has anyone done this full treatment to a Cruiser?

 

[01138lex]

I keep coming back to this. The more research I do, the more it sounds like there are really three things that need to be done. First is the anti-vibration material (Dynamat or similar), then some type of isolating barrier - typically a closed cell foam - and then a sound blocking layer, typically Mass Loaded Vinyl. Has anyone done this full treatment to a Cruiser?

I did the full meal deal on my ride. Its labor intensive (14+hrs), a lot of money in materials (~1200cdn), and the return on investment is low. It comes down to how much you value cabin noise. I did a double skin on all the doors inner/outer. It adds a significant amount of heft to the doors. Double up on the rear fenders.

Dont buy cheap stuff; your car will smell like asphalt and that s*** will melt off your panels in the summer. Pay once with good materials and be done.
Dynamat extreme, Soundskin, Noico. In that order in regards to cost.

I did my dynamat only because we were ripping out the interior already for the new audio setup.