Low frequency Dampers - do these things work?

[TerryMason]

I was watching Truck U last night, and they talked about low frequency dampers. These are supposed to get rid of the low moan / groan that you can sometimes here when you brake. It sounded like snake oil to me, but they said that it's becoming standard equipment on many new cars.

Do these things actually work? If so, how?

New low frequency dampers help to eliminate the "moans," "groans" and "squeals" common to the rear calipers of certain applications. NAPA Brakes low frequency dampers incorporate a unique sound and energy absorbing compound that is scientifically 'tuned' to the frequency found on the applications shown.

 

[superj]

We use vibration and harmonic damnpers in helicopters. The harmonic ones just look like rings, to me, but i am told if the gears were installed back into the transmission without them, the transmission gears would come appart from the frequencies being at some certain tune.

I tested them, the back yard way. I tapped the gears with a piece of aluminum and each hear rang, like when you tap a cymbol for drums. They would hold the ring for a few seconds.... and these are big 40 pound gears. Then i installed the dampner ring and tapped the gears.

Nothing, just a tink.

So they work on gears in helicopter

 

[superj]

And the engines have onw of the front of the crank, but we call them harmonic balancers. Its the same thing

 

[TerryMason]

Cool. It doesn't sound like a real problem that I'd spend money on (for our Jeeps that is), but it's interesting.

 

[cougarlasch]

some toyota's have them on the exhaust and grand marquis and crown vic.