The length of your tailpipe from muffler back matters a lot to the rpm where Drone is most severe. Just as a Church Organ makes different musical notes when different length pipes get air blown through them, so will your exhaust make annoying music.
Very roughly, if drone was severe at 2000 rpm, and much less at 1500 rpm,
then your tailpipe length needs to increase
2000 divided by 1500
4/3 rds
Other things come into play here, such as the temperature of the exhaust gas, which will be higher the more the trottle is opened.
You could experiment to find the added length that snuffs out drone.
Buy two ninety degree fittings, and two lengths of either solid or flexible corrigated pipe,
and add maximum length for side outlet style exhaust,
then cut off about two inches at a time untill the exhaust note suits you.
Drive up steep hills to demonstrate how a more open throttle changes exhaust temperature and therefore drone.
The quietest set up for low drone in the 1200 to 2200 rpm range is usually large "Helmhertz Trap" mufflers mounted cross ways near the rear bumper fed by as long as possible tailpipes. T-Traps of closed stub pipes the right length can also kill drone at a particular rpm.
Really well stated. Furthermore, the tub of your unibody car is one big musical instrument as well. When the mufflers resonate, all that harmonic vibration will make the car itself drone. In fact, much of what you're hearing is the car! If you haven't gone the dynamat route this will help a bit but not completely. The last car that I installed dumps on was longer ago than I'd like to say. I found a great solution for the drone. I purchased a pair of Thrush resonators and installed them after my mufflers and added about a foot of pipe beyond them so the dumps dropped right in front of the rear axle and it completely solve my problem. Before I installed the resonators, the drone was unbearable like yours at a certain RPM. Second gear was a real beotch. Just remember that the harmonics of every exhaust system are different, so what worked for me may not work for you.
If you want to see how harmonics work go inside a walking tunnel of decent length with smooth surfaces. Stand in the middle. Then start singing a low note and start raising the pitch. At some point your voice will begin to make the tunnel start ringing really loud!
