That LX Charger underside picture shows many “tricks” to get rid of drone while keeping back-pressure low. There are also aerodynamic tricks that older cars did not have.
It would be even better if we could see inside the big center muffler AND inside the smaller two “resonator” type units near the rear bumper.
There might be T-stub pipes hidden inside.
I also would not be surprised if the distance between the two exhaust ends is critical too. It might partially cancel a particular drone noise at a particular RPM.
Is there any Sales Literature that states that the LX Charger factory Radio/CD/ MP3 player has Bose-like noise cancellation electronic circuits?