Step 1. Resonance frequency.
Enter engine revs where drone appears.
Choose your type of engine.
Get resonance frequency of your exhaust system.
Step 2. Parameters of the Helmholtz muffler.
The speed of sound depends on temperature. Choose temp (or use default settings — 200°С)
Enter the resonance frequency of your exhaust system.
Enter the diameter of the connection tube. (S)
Enter the volume of the chamber. (V)
Get your connection tube length ! (L)