A coincidence dip can make the heavier panel worse
Supplied working report; original verdicts not validated.
Review status: Needs review. This is an archival source note, not a passed proof.
notes.md
# A coincidence dip can make the heavier panel worse **Verdict: Supported.** A 15.0 kg/m2 glass panel falls 5.4 dB below a 10.0 kg/m2 plasterboard panel near 2088 Hz, because the heavier panel's coincidence dip sits at that frequency; mass alone would always favour the heavier panel. ## Design Single-leaf mass law plus a 10 dB coincidence notch at fc = c0^2/(1.8 cL t); five materials from 6 mm glass to 100 mm concrete, transmission loss computed from 50 to 8,000 Hz. ## Result - Materials modelled: 5 - Inversions found: 3 - Largest mass ratio inverted: 1.1x - Notch depth assumed: 10 dB ## Limits - The notch depth and width are assumed, not measured; a shallower dip removes the inversion for small mass differences. - Single-leaf theory ignores studs, cavities, linings and flanking paths, which dominate real partition performance. - The coincidence formula assumes a homogeneous isotropic plate and normal incidence mass law; field incidence lowers the whole curve. - Only five illustrative materials are used, so this demonstrates the mechanism rather than ranking real products.