A crosscorrelation-based method for improved visualization of infant cry vocalizations

The plots generated by this method are well suited to the visual identification and determination of the vocal fundamental frequency (F ₀). This new method calculates the crosscorrelation values between adjacent segments of the digitized cry. These values can then be plotted in a three-dimensional pattern of intensity versus frequency versus time, in a manner similar to that of the spectrogram. This plot, called a crosscorrelogram, indicates periodicity by the presence of strong peaks and valleys. These crosscorrelation values can be further manipulated to determine which peak, at any given time, corresponds to the correct F₀. Rapid changes and the progression of the fundamental frequency over time can be tracked as well, achieving an accuracy and granularity that was not previously possible when using traditionally successful and popular F₀ extraction techniques such as cepstral analysis or the linear predictive coding (LPC) based methods. In addition, the crosscorrelogram visually provides more detail regarding F₀ evolution than does the spectrogram, since the latter uses a fixed window size that includes a varying number of pitch periods per window, for narrowband spectrograms, resulting in an average or “smeared” F₀ value being displayed