Remove DC component

The algorithm removes any DC offset in the signal. This is a very important step because the zero-crossing rate of the signal is calculated and plays a role in determining where unvoiced sections of speech exist. If the DC offset is not removed, we will be unable to find the zero-crossing rate of noise in order to eliminate it from our signal.

Threshold determination: via computing average magnatude and zero-crossing rates.

Compute the average magnitude and zero-crossing rate of the signal as well as the average magnitude and zero-crossing rate of background noise.

The average magnitude and zero-crossing rate of the noise is taken from the first hundred milliseconds of the signal.

The means and standard deviations of both the average magnitude and zero-crossing rate of noise are calculated, enabling us to determine thresholds for each to separate the actual speech signal from the background noise.

Signal speration from noise. Done using tresholds from previous step.

At the beginning of the signal, we search for the first point where the signal magnitude exceeds the previously set threshold for the average magnitude. This location marks the beginning of the voiced section of the speech.

starting point of speech = first point a sample's magnitude > noise magnatude thershold.

1. From this point, search backwards until the magnitude drops below a lower magnitude threshold.
2. From here, we search the previous twenty-five frames of the signal to locate if and when a point exists where the zero-crossing rate drops below the previously set threshold. This point, if it is found, demonstrates that the speech begins with an unvoiced sound and allows the algorithm to return a starting point for the speech, which includes any unvoiced section at the start of the phrase.

Repeat above steps for the end of the speech signal.