Car is so loud on inside. Helmholtz branch (1/4 wave) resonator?
12-07-2016, 09:38 AM
#21
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So the running hypothesis at the moment is that the hangers I'm using is transmitting the noise into the trunk and cabin on the midpipe/muffler. The Miata Roadster shifter kit came with new sound deadening material for the boot and this has helped a lot with heat I used to feel radiating. But sound is unaffected. I also don't have that felt material under my carpet because base model. That would be a project for a new carpet install to get MLV and some CCF to decouple.
I have yet to switch back to rubber mounts with hose clamp and zip ties, but the car is definitely quieter on the outside. I took some acoustic foam and cut blocks off to pack under the package tray cover by the rear sway bar mount points and this surprisingly helped. I feel as though I placed the urethane mounts on the car for a reason because 3" pipe was banging around everywhere over wiggles and jiggles, but I may leave the rear most two mounts urethane while switching the rest back to rubber. Using the mega 4th mount made by Shuiend, and the stocker by the muffler tip, the urethane bushing should allow some transverse stiffness but due to stiffer boundary conditions being at the end of the car, and not attached to the subframe where it can vibrate midplane, shouldn't introduce as much vibration into the trunk where it may hit that nice ~113Hz resonance. I am planning to reupholster the package tray since I switched roll bars and will probably refresh the deadening there.
I have yet to switch back to rubber mounts with hose clamp and zip ties, but the car is definitely quieter on the outside. I took some acoustic foam and cut blocks off to pack under the package tray cover by the rear sway bar mount points and this surprisingly helped. I feel as though I placed the urethane mounts on the car for a reason because 3" pipe was banging around everywhere over wiggles and jiggles, but I may leave the rear most two mounts urethane while switching the rest back to rubber. Using the mega 4th mount made by Shuiend, and the stocker by the muffler tip, the urethane bushing should allow some transverse stiffness but due to stiffer boundary conditions being at the end of the car, and not attached to the subframe where it can vibrate midplane, shouldn't introduce as much vibration into the trunk where it may hit that nice ~113Hz resonance. I am planning to reupholster the package tray since I switched roll bars and will probably refresh the deadening there.
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12-07-2016, 09:57 AM
#22
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So the running hypothesis at the moment is that the hangers I'm using is transmitting the noise into the trunk and cabin on the midpipe/muffler. The Miata Roadster shifter kit came with new sound deadening material for the boot and this has helped a lot with heat I used to feel radiating. But sound is unaffected. I also don't have that felt material under my carpet because base model. That would be a project for a new carpet install to get MLV and some CCF to decouple.
I have yet to switch back to rubber mounts with hose clamp and zip ties, but the car is definitely quieter on the outside. I took some acoustic foam and cut blocks off to pack under the package tray cover by the rear sway bar mount points and this surprisingly helped. I feel as though I placed the urethane mounts on the car for a reason because 3" pipe was banging around everywhere over wiggles and jiggles, but I may leave the rear most two mounts urethane while switching the rest back to rubber. Using the mega 4th mount made by Shuiend, and the stocker by the muffler tip, the urethane bushing should allow some transverse stiffness but due to stiffer boundary conditions being at the end of the car, and not attached to the subframe where it can vibrate midplane, shouldn't introduce as much vibration into the trunk where it may hit that nice ~113Hz resonance. I am planning to reupholster the package tray since I switched roll bars and will probably refresh the deadening there.
I have yet to switch back to rubber mounts with hose clamp and zip ties, but the car is definitely quieter on the outside. I took some acoustic foam and cut blocks off to pack under the package tray cover by the rear sway bar mount points and this surprisingly helped. I feel as though I placed the urethane mounts on the car for a reason because 3" pipe was banging around everywhere over wiggles and jiggles, but I may leave the rear most two mounts urethane while switching the rest back to rubber. Using the mega 4th mount made by Shuiend, and the stocker by the muffler tip, the urethane bushing should allow some transverse stiffness but due to stiffer boundary conditions being at the end of the car, and not attached to the subframe where it can vibrate midplane, shouldn't introduce as much vibration into the trunk where it may hit that nice ~113Hz resonance. I am planning to reupholster the package tray since I switched roll bars and will probably refresh the deadening there.
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12-07-2016, 01:23 PM
#28
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Here's the relevant spot in EO2K's thread. I looked it up because I was curious.
https://www.miataturbo.net/build-thr...9/#post1232036
https://www.miataturbo.net/build-thr...9/#post1232036
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12-10-2016, 07:32 PM
#32
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Have you tried blocking the two tunnels on either side fo the gas tank?
Apparently a lot of noise comes up through the trunk, bounces around, and gets sent into the cabin via those tunnels. I've read some threads of people filling them will insulation with good results.
Disclaimer: I haven't done this myself.... yet
Apparently a lot of noise comes up through the trunk, bounces around, and gets sent into the cabin via those tunnels. I've read some threads of people filling them will insulation with good results.
Disclaimer: I haven't done this myself.... yet
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12-10-2016, 07:40 PM
#33
Have you tried blocking the two tunnels on either side fo the gas tank?
Apparently a lot of noise comes up through the trunk, bounces around, and gets sent into the cabin via those tunnels. I've read some threads of people filling them will insulation with good results.
Disclaimer: I haven't done this myself.... yet
Apparently a lot of noise comes up through the trunk, bounces around, and gets sent into the cabin via those tunnels. I've read some threads of people filling them will insulation with good results.
Disclaimer: I haven't done this myself.... yet
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