Helmholtz resonator with variable resonance frequency for damping IC engine air intake or exhaust gas noise uses controlled stops for altering neck opening cross-sections

摘要

The Helmholtz resonator has a resonance chamber (1) and a tubular neck region (2) containing at least 2 openings (4,5) at different relative spacings from the resonance chamber, each exhibiting a variable opening cross-section (d1,d2) under control of a respective stop (8,9), for varying the resonance frequency in dependence on the engine revs.