www.gusucode.com > 声音的处理有：LPC，FFT，共振峰，频谱源码程序 > siganlandsystemusingMatlab/SSUM/library/zero_crossings.m

    function Nzeros = zero_crossings(signal)

    Nzeros = 0;
    for i=2:length(signal),
        if (sign(signal(i)) ~= sign(signal(i-1)))
            Nzeros = Nzeros + 1;
        end
    end