47-55.1 Acoustic glass.

[mick53]

My truck is going to be loud. I don't want teenage loud exhaust but I need flow. I have electric cutouts. I figure between the 4-71 blower and the Frankland quick change rear end with straight cut gears she's going to wine a bit. I plan to go to great extremes to soundproof my cab. I have been looking into acoustic glass for the windows. It's not terribly expensive and is basically laminated glass with the plastic in the middle a sound dampener. It seems like that would be unsafe to put on the side windows because you couldn't break it out. Most of the noise probably comes from the front anyway. Am I way off track here? Any thoughts would be appreciated. Thank you.

[joedoh]

sound gets in the cab two ways:

directly, through openings, even small ones.

sympathetically, through resonance.

for direct propogation you seal the cab, thats why the cab/door seals make such a big difference, the continuous gap really lets a lot of wind and other noise in. soound waves dont penetrate a sealed cab.

for resonance, you have to look at what is resonating. remember being a kid with your ear on a railroad track? that is resonance. in a truck it is a sound wave that hits a panel and makes it vibrate in a sympathetic way. the loudest frequency of a panel is called the resonant frequency, it is literally where the smallest input makes the panel vibrate the most. to dampen this sound you find these big flat panels that are vibrating and you add mass. most times though the addition of weight. this is why it doesnt matter if you buy super deluxe sound deadener pro extreme super mat at 45 dollars a roll or peel and seal from homer derpt for 16 dollars a roll, mass is mass. adding mass LOWERS the resonant frequency, and lower frequencies take more input power to be produced (if you ever bought a subwoofer amp you know this). adding more mass will lower the resonant frequency further, but there is a diminishing return, so layer on layer of mat wont make much difference, usually the first layer is enough.

another way to dampen resonance is to put absorptive material on flat hard surfaces, usually acoustic foam that breaks up the reflection of sound waves that have made it in the cab. most people cant put foam on the dash though so usually a nice thick jute under teh carpet is enough absorptive material.

why am I telling you all of this? because glass is really hard and will have a really high resonant frequency, its probably likely that the first steps, sealing the cab and damping resonance will be far more effective in controlling noise than worrying about sound coming through the glass. chances are the glass as a last step will probably not make much difference even in a really damped cab, and will make absolutely no difference in a cab that has air leaks or no other damping material added. so do the first things first.

a long time ago lexus had a commercial about using that double layer glass, I think they were improving the interior sound level from 72db to something like 66db at 60mph. 72db in a moving car is already seriously quiet, where you can hear your daughter sulking in the back seat, 66db is two orders of magnitude quieter than that.


cliff notes: TL/DR: glass isnt where you should start and you may find it doesnt help anyway.

[mr48chev]

Every AD and TF truck comes stock with laminated glass. I don't understand the nonsense of Can't break it to escape business. Thinking on it I don't think they put tempered glass in side glass until the 80's with curved glass.

Still there are glass shops that will cut glass to spec and send it off to be tempered as I have to have done on my truck. One might be able to get someone to do a heavier tempered glass that way.

[Wrenchbender Ret]

Great info Joedoh. Thanks for sharing it with us.
Where in the heck is Doodah Kansas?

George

[joedoh]

doodah has been used interchangeably for wichita for years, it got popular with the local paper columnist bob getz in the 80s and 90s but was a thing long before that

[mr48chev]

I remember Wichita from a few years ago when we were down there on the 4th and I some kid with a donked out Caprice bust a brand new rim and tire on a pothole three blocks from the tire store I saw him pull out of with the paper sticker still on the tire.
I still get emails from the Goodyear store there on the other side of town that fixed my tire on the 4th. Hit a show in Park city on the 4th that year.

Back to the original subject I think Joe pretty well hit it. Correct sound deadener, properly placed and well sealed openings. There is a lot of info on the subject on the audiophile forums. They don't like the sheet metal vibration interfering with sound quality on high end systems. The reason you hear some of these cars that the kids who have a big amp big sub and not much for other speakers buzz from the vibration when they go down the road with it cranked up and you hear the metal vibrate as much as the sound.

[_Ogre]

Originally Posted by mick53

I don't want teenage loud exhaust but I need flow. I have electric cutouts.

then remove the cutouts

i tried overkill on soundproofing, it may have helped some, but truk is deafening from wind noise above 60mph
i counter wind with stereo volume

[mick53]

Originally Posted by joedoh

sound gets in the cab two ways:

directly, through openings, even small ones.

sympathetically, through resonance.

for direct propogation you seal the cab, thats why the cab/door seals make such a big difference, the continuous gap really lets a lot of wind and other noise in. soound waves dont penetrate a sealed cab.

for resonance, you have to look at what is resonating. remember being a kid with your ear on a railroad track? that is resonance. in a truck it is a sound wave that hits a panel and makes it vibrate in a sympathetic way. the loudest frequency of a panel is called the resonant frequency, it is literally where the smallest input makes the panel vibrate the most. to dampen this sound you find these big flat panels that are vibrating and you add mass. most times though the addition of weight. this is why it doesnt matter if you buy super deluxe sound deadener pro extreme super mat at 45 dollars a roll or peel and seal from homer derpt for 16 dollars a roll, mass is mass. adding mass LOWERS the resonant frequency, and lower frequencies take more input power to be produced (if you ever bought a subwoofer amp you know this). adding more mass will lower the resonant frequency further, but there is a diminishing return, so layer on layer of mat wont make much difference, usually the first layer is enough.

another way to dampen resonance is to put absorptive material on flat hard surfaces, usually acoustic foam that breaks up the reflection of sound waves that have made it in the cab. most people cant put foam on the dash though so usually a nice thick jute under teh carpet is enough absorptive material.

why am I telling you all of this? because glass is really hard and will have a really high resonant frequency, its probably likely that the first steps, sealing the cab and damping resonance will be far more effective in controlling noise than worrying about sound coming through the glass. chances are the glass as a last step will probably not make much difference even in a really damped cab, and will make absolutely no difference in a cab that has air leaks or no other damping material added. so do the first things first.

a long time ago lexus had a commercial about using that double layer glass, I think they were improving the interior sound level from 72db to something like 66db at 60mph. 72db in a moving car is already seriously quiet, where you can hear your daughter sulking in the back seat, 66db is two orders of magnitude quieter than that.


cliff notes: TL/DR: glass isnt where you should start and you may find it doesnt help anyway.

Great info, thanks. would things like isolating the cab and dog house with dampeners be worth the effort?

[joedoh]

Originally Posted by mick53

Great info, thanks. would things like isolating the cab and dog house with dampeners be worth the effort?

your cab and doghouse could/should be insulated with body mounts. a proper body mount should be the isolation type where there is no path between the frame and the cab for vibration except through rubber. some guys clamp the frame down with a bolt and washers with a piece of rubber in between and that rubber is not isolated, the vibration goes straight through the bolt to the cab.

[mick53]

Thanks for the info. I'm a long ways from that point just thinking ahead. I'm working 500 miles from my truck for a couple of months so all I can do is learn and plan.

[joedoh]

Originally Posted by mick53

Thanks for the info. I'm a long ways from that point just thinking ahead. I'm working 500 miles from my truck for a couple of months so all I can do is learn and plan.

nothing wrong with that, I call it "bench racing" and its cheaper for sure. just dont paint yourself into a corner with buying parts for the 10 decisions down the road, and you will be fine!