Partition mass provides isolation at higher frequencies until coincident resonances degrade it

Evidence

The solution is to have two or more partitions that are independent of each other. If the two partitions are truly independent, the total attenuation, or effective sound isolation, is the product of the attenuations of individual partitions, that is, the dB attenuation is the sum of the dB attenuations of the individual partitions. In practice, the partitions are not independent, although the isolation is improved dramatically, but not as much as would be predicted by simply summing the dB attenuations. Coincidence resonances also reduce the effectiveness of a partition, and it is important to ensure that the two partitions have different resonances. This is most easily assured by having them made with either a different thickness or a different material. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2119 (#corroborates, via linked claim)

Categorization

• corroborated: 2 independent passages support this claim
• XREF: connects to: Mass dominates impedance at high frequencies, stiffness at low frequencies — Eric J. Heller, Why You Hear What You Hear- An…, 87; Partition sound attenuation rises with frequency except at coincident resonances, which damping reduces; Room resonances shift from isolated to overlapping at the Schroeder frequency (+3 more)

Broader Connections

• Room resonances shift from isolated to overlapping at the Schroeder frequency #expands (0.85)
• Independent partitions sum their attenuation in decibels #corroborates (0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2119
• Modal absorption is frequency dependent, stretching decay time at standing-wave frequencies #expands (0.80)
• Adding damping to a resonance paradoxically makes it more audible by widening its bandwidth #epitomizes (0.75)