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Diagrams showing the geometry and the relevant variables and constants of the problem for (a) flat rigid piston and (b) for a periodically corrugated rigid piston. The radiated sound power is labeled as and for each case.
Time averaged quadratic pressure field ( in normalized units) of a flat (a) and (b) a corrugated piston having ten cavities (), d = 0.3 a, and h = 0.71 a at a λ = 0.9 (c) NPL in (dB) along z/D at the radiation axis.
(a) Radiation efficiency in (dB) of a corrugated piston with proportions h/a = 1.71 and a hole filling fraction f = 0.3 calculated using different models (see labels) as a function of . (b) Magnitude (solid curve, left vertical axis) and phase (dashed curve, right vertical axis) of the average velocity at the aperture entrance calculated with the two-dimensional modal expansion as a function of .
Radiation efficiency in (dB) as a function of of a corrugated piston (a) having f = 0.1 for different h/a ratios and (b) for fixed h/a = 0.71 and different hole filling fractions f.
(a) Radiation efficiency in (dB) as a function of for a corrugation having h/a = 0.71 and f = 0.52 calculated for infinite and finite pistons. The arrow shows the point at which the fields in (b) and (c) have been calculated. Normalized pressure level fields in (dB) for a (b) corrugated and (c) flat piston at .
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