How to read fetch wav file one by one in matlab?

this is my Matlab code, I want to read .wav file from the same file or another file.

str=['1.wav';'2.wav';'3.wav';'4.wav';'5.wav';];
for i=1:5
    [y, fs]=wavread(str(i));
    a = miraudio(str(i));
    z = mirzerocross(a)
    close all
end

it gives me error like.. Error using TRYFINAL (line 1) Error using vertcat Dimensions of matrices being concatenated are not consistent.