Mass-Air-Mass Resonance

Mass-air-mass resonance is the fundamental resonant frequency of a double-leaf partition system, where the two panel leaves act as masses and the enclosed air cavity acts as a spring. At this frequency, insulation performance drops significantly—often below that of a single leaf of equal total mass. The resonant frequency depends on the surface masses of both leaves and the cavity depth, typically falling in the 50–200 Hz range. Below this frequency, the double-leaf system behaves as a single combined mass. Above it, performance improves rapidly at approximately 18 dB per octave (compared to 6 dB/octave for a single leaf). Design strategies include using the widest practical cavity to lower the resonant frequency, filling the cavity with absorptive material, and using different leaf masses to spread the resonance. Mass-air-mass resonance is the key design parameter for all cavity wall and double-glazing systems.