Measuring time delay of audio signals
Are you sure you shouldn't be using numpy.correlate instead of numpy.convolve?  To estimate delay, you want to cross-correlate your signals, not convolve them.  You'll possibly end up with a much larger delay by convolving.

Trying something simple:

x = [1, 0, 0, 0, 0 ];
y = [0, 0, 0, 0, 1 ];
conv = numpy.convolve(x,y); 
conv
array([0, 0, 0, 0, 1, 0, 0, 0, 0])
corr = numpy.correlate(x,y,"full");
corr
array([1, 0, 0, 0, 0, 0, 0, 0, 0])