One pane of a double-glazing unit is thick glass with

PHYSICS · Subjective · Fermi University Physics · Oscillations, Waves & Acoustics · Fluids & Continuum Physics · Vibrating bodies, musical and architectural acoustics

Bending, Ringing, Breaking and Flowing, Ch Vibrations of rods, beams and plates

Problem

One pane of a double-glazing unit is 4 mm4\,\mathrm{mm} thick glass with E=70 GPaE = 70\,\mathrm{GPa}, ν=0.22\nu = 0.22 and ρ=2500 kg m−3\rho = 2500\,\mathrm{kg\,m^{-3}}. Taking the speed of sound in air as c=343 m s−1c = 343\,\mathrm{m\,s^{-1}}, find the coincidence frequency fc=(c2/2π)ρh/Df_c = (c^2/2\pi)\sqrt{\rho h/D} of this pane, where D=Eh3/[12(1−ν2)]D = Eh^3/[12(1-\nu^2)] is the flexural rigidity. State whether this pane's coincidence dip lies at a higher or lower pitch than the 2.0 kHz2.0\,\mathrm{kHz} dip of a 6 mm6\,\mathrm{mm} pane of the same glass.

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