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I have an exhaust that drones with the vehicle. However, outside, it's not a loud exhaust. So my assumption is the vibrations are transmitted into vehicle interior via the points of contact - in this case the rubber exhaust hangers.

The exhaust hangers are used fit very tight and are somewhat stretched, so is my theory correct - does the pre-stretch on the hangers allows more vibration transmission into the vehicle?

enter image description here

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    $\begingroup$ Ask vehicle maintenance and repair se $\endgroup$ – user4139 Sep 6 '18 at 19:49
  • $\begingroup$ Can’t see much rubber there, a better picture from a different angle or change the hanger so you get a decent rubber mount. $\endgroup$ – Solar Mike Sep 6 '18 at 19:58
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    $\begingroup$ Rubber hangers isolate most of the sound. Look for some place where exhaust component is touching the frame. It may only occur with the weight of a person in the car. $\endgroup$ – blacksmith37 Sep 6 '18 at 21:06
  • $\begingroup$ @Muze My question is more about mechanical properties of the rubber hanger. $\endgroup$ – Alexus Sep 7 '18 at 20:05
  • $\begingroup$ @SolarMike The triangular part of the picture where metal hangers are attached to is rubber. It has 3 holes - one on top and 2 on the bottom. Top hole connects to metal rod on car body, bottom connect to exhaust. $\endgroup$ – Alexus Sep 7 '18 at 20:06
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Consider a metal rod. You put your ear to one end. Someone "pings" the other. You will hear the ping thru the metal. Now add a wad of cotton balls at your end and repeat. Press your ear firmly on the cotton. The sound will be muffled if it comes thru at all.

When your vibrating exhaust is attached directly to the car, the car picks up and can amplify the sound. To avoid the problem, you must decouple the vibrations generated by the exhaust from reaching the car. You have two approaches. You can add the equivalent of a non-transmitting medium between the exhaust and the car body. Rubber acts as a vibration isolation medium. An appropriately designed spring can do the same. The other approach is to reduce the contact area between the exhaust and the car. By example, at the point where the exhaust runs under the car, hang it by a strong-enough wire rather than attaching it with clamps to the car body.

This is the theory. The best practice is likely found by researching trade journals or chatting with folks from car shops that do the installations.

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  • $\begingroup$ Seeing as the exhaust waveform starts at the exit valve of the cylinders, one first must verify that the engine block and the exhaust headers are not the primary source $\endgroup$ – Carl Witthoft Sep 7 '18 at 18:20
  • $\begingroup$ @CarlWitthoft Replacing exhaust with a better muffled and resonated one seems to eliminate the drone. So it's not the engine. Also, the stock exhaust fits much looser inside the holes of the rubber mount. $\endgroup$ – Alexus Sep 7 '18 at 20:04

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