Audio Separation of .wav signal
If you are using Matlab, the plots looks like Matlab, you can use indexing directly to get a threshold value:

% 'time' is the time series
% 'signal' is the signal itself
idx = signal &gt; 0.2;
plot(time(idx), signal(idx));


You are not clear on what you're trying to achieve, but there could be some information found in the frequency spectrum, so that you could do for example a fourier transform on the signal.