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especially a ported box with a tuned length port. You want to match resonant frequencies to cancel out of ehnace areas of the sound for the desired overall effect. This is also similar to the tuning process and calculations for a 2-stroke exhaust system with expansion chambers. You tune the diameters and lengths of the expanding, and contracting cones as well as the "straight" section in between to the reflected exhaust gasses pulses so that you get a high pressure zone just outside of the exhaust port, helping to generate the highest in-cylinder pressures as the piston closes the ports, and the lowest(actually slightly negative) pressure outside the port as the piston uncovers the port for maximum scavenging.
Mike ------------------------------------------------------
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