Features

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LPC Analysis, Waterfall Plots, Vowel Space Plots

In addition to research-grade FFT spectrograms, the SpeechStation2 offers LPC-based spectrograms, formant track plotting, autocorrelation-based pitch (f0) tracks, 3D and line waterfall plots and vowel space plots.

Pitch tracks are computed rapidly and superimposed in red directly on the spectrogram at ten times their calculated frequency, for clarity. This display multiplier can be set by the user. In addition, pitch tracks can be saved to a text file for analysis and processing by other programs.

Waterfall plots are available in four formats: the most impressive is the shaded, gradient illumination plot developed by Sensimetrics, to which Dr. J. M. Pickett has given the elegant designation, perspectrogram. The default version of this plot is in black-and-white; the illustration at right shows the color option. In addition, an inverse-shaded version, a high-resolution line version, and a low-resolution line version, are available, the last-listed corresponding to the waterfall plots normally used for publication. The parameters, including FFT analysis window type and length, pre-emphasis, vertical scale and dynamic range of the plot are fully adjustable. The segment of sound data used to make the plot can be heard through the system loudspeakers by clicking on a button provided. The gradient illumination plots reveal a wealth of detail with much greater clarity than conventional waterfall plots. Click on the illustration to see the plot enlarged.

The new vowel space plot produces a point plot of the trajectory formed by the intersection of formant values or other resonances in the voice or transmission channel. The trajectory represents articulation as single-valued and time-varying. Time resolution is adjustable, and the display can be toggled between a point-by-point plot and a density plot that shows the distribution of plotted points as gray-scale elements in a 32x32 grid.