This removes noise in the signal. Double high pass filter the signal. This removes the very low freqency swell that is often observed in laryngograph waveforms. Double filtering is performed to reduce any phase shift beween the input and output of the filtering operation. Calculate the delta signal.
Low pass filter the delta signal.
Some noise may still be present in the signal, and this is removed by further low pass filtering. Experimentation has shown that simple mean smoothing is often more effective than FIR smoothing at this point. The parameter mo is used to specify the size of the mean smoothing window. Double filtering is again used to avoid phase distortion. Pick zero crossings.