Deeper rear cavities and heavier panels lower a resonant absorber’s tuning frequency

Evidence

The resonant characteristics of these absorbers enable them to be tuned to low frequencies and so allow them to have absorption characteristics that complement those of porous absorbers. The peak absorption frequency of a resonant absorber is a function of the space behind the absorber and the effective mass of the front panel. To use an analogy with a spring and weight, the rear cavity acts like a spring whose stiffness is inversely proportional to the depth of the cavity, and the effective mass per unit area of the front panel determines the size of the weight. As the spring gets less stiff and the effective mass becomes greater, the resonant frequency drops. Thus deeper rear cavities result in lower resonances for both types. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2052

The resonant characteristics of these absorbers enable them to be tuned to low frequencies and so allow them to have absorption characteristics which complement those of porous absorbers. The peak absorption frequency of a resonant absorber is a function of the space behind the absorber and the effective mass of the front panel. To use an analogy with a spring and weight, the rear cavity acts like a spring whose stiffness is inversely proportional to the depth of the cavity and the effective mass per unit area of the front panel determines the size of the weight. As the spring gets less stiff and the effec­ tive mass becomes greater, the resonant frequency drops. Thus deeper rear cavities result in lower resonances for both types. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2103

Categorization

• XREF: The spring-mass analogy is the same oscillator model that underlies Helmholtz resonators and loudspeaker box tuning. — connects to: Low diaphragm mass does not improve transient response in panels; Heavier panel absorbers resonate at lower frequencies — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2054; Helmholtz resonance is the trapped-air cavity resonance exploited in perforated-panel absorbers (+2 more)
• corroborated: 5 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2052; David Howard, Jamie Angus, coustics and Psychoacoustics, 2103

Broader Connections

• Heavier panel absorbers resonate at lower frequencies #corroborates (1.00) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2054
• Helmholtz resonance is the trapped-air cavity resonance exploited in perforated-panel absorbers #expands (0.85)