function [acoustic, radiation] = plate_radiation(freqs, volume_part, params, P)
% PLATE_RADIATION  Pressure at the microphone per unit modal acceleration.
%
%   [acoustic, radiation] = plate_radiation(freqs, volume_part, params, P)
%   gives, for each mode, the coefficient a such that the mode's contribution
%   to the pressure at the microphone is a * q_tt(t):
%
%     a = rho_air / (2 pi r) * V * sqrt(min(1, f / f_c)),
%
%   where V is the mode's volume participation (the integral of the mass-
%   normalized shape over the plate: a compact-source estimate for a
%   microphone on the plate's normal at distance r), and the square-root
%   factor stands for the front/back cancellation of a small unbaffled plate
%   below its coincidence frequency f_c (plate_setup).  It is a smooth
%   estimate of the radiation efficiency, not a solution of the diffraction
%   problem, so the output is meaningful in timbre and decay while its
%   absolute level is only approximate.

freqs = freqs(:)';
volume_part = volume_part(:)';
radiation = sqrt(min(1, max(freqs / P.critical_frequency, 1e-4)));
acoustic = params.mic.air_density / (2 * pi * params.mic.distance) * volume_part .* radiation;
end