midnightsun
Active Member
- Joined
- January 13, 2014
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- 96
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- Year, Model & Trim Level
- 2022 Explorer ST
US special forces for instance use noise cancellation on "silent" vehicles. So how do we apply this to a car exhaust? We flip the sound out of phase and have it crash back into its self.
How do we do that? Easiest is building a side branch resonator / 1/4 wave resonator.
Note * The diameter of the side branch should be equal to the diameter of the main pipe *
First we find the frequency of the drone. Using your phone you can download a Spectrum Analyzer app. Then while driving around record the frequency the drone is being produced at and the RPM. It will be a fairly low frequency say 135HZ and below.
Note * Some Cell phones have crappy mics so you might need a good mic to capture the correct frequency."
Picture below is just an example and not my Explorer.
Now that you have this data you can have an exhaust pipe chamber or chambers built that will cancel the frequencies that annoy you.
Pictures i found showing examples of this.
Muffler companies such as Corsa try to do this in the muffler will sometimes limited success and add a large cost.
So for about $70 you can have a muffler shop weld you in a side branch resonator chamber.
So some key points. Notice the 1/4 chambers are angled. This is because water can collect in them. You want the water to be easily removed by gravity.
How do we do that? Easiest is building a side branch resonator / 1/4 wave resonator.
Note * The diameter of the side branch should be equal to the diameter of the main pipe *
First we find the frequency of the drone. Using your phone you can download a Spectrum Analyzer app. Then while driving around record the frequency the drone is being produced at and the RPM. It will be a fairly low frequency say 135HZ and below.
Note * Some Cell phones have crappy mics so you might need a good mic to capture the correct frequency."
Picture below is just an example and not my Explorer.
Now that you have this data you can have an exhaust pipe chamber or chambers built that will cancel the frequencies that annoy you.
Pictures i found showing examples of this.
Muffler companies such as Corsa try to do this in the muffler will sometimes limited success and add a large cost.
So for about $70 you can have a muffler shop weld you in a side branch resonator chamber.
So some key points. Notice the 1/4 chambers are angled. This is because water can collect in them. You want the water to be easily removed by gravity.