The trick to resonance (or sound) tuning of the IM is to have these maximally amplified waves arrive at the intake valve just as it opens . The basic mechanism of intake manifold "tuning" or design is to provide high pressure at the intake valve so that the mass flow rate into the cylinder is boosted at a given engine speed or rpm. We do this "tuning" by changing the IM runner length and diameter (area).
Neat link:
Runner Length Tuning