% hz2mel - Convert frequencies from Hertz to mel scale.
%
% hz2mel :: 
%    [[D]->nonneg] ~'any shape array of frequencies in Hz'
% -> [[D]->nonneg] ~'corresponding array of frequencies in mels'.
%
% Mel scale is approx linear below 700 Hz, and approx log above.
% Overall scaling fixed so that 1000 mel = 1000 Hz.
function m=hz2mel(f), m=2595*log10(1+f/700);
