The display in the left panels of Figures 1, 3, 4, & 5 is the spectrogram of the microphone signal. This display provides a framework that locates the power spectrum and waveform displays within the sound as it is perceived. Like the waveform display, it shows time from left to right. The time scale, however, is on the order of the musical phrase, showing up to eight seconds, rather than the few glottal cycles of the high time-resolution waveform display. The frequency dimension — the horizontal axis in the power spectrum — is the vertical axis in the spectrogram The relative intensity of the various frequency components is indicated by a color scale or, alternatively, by shades of gray.

Many important observations on the singing voice, such as the rate and extent of vibrato, the duration of legato-disrupting consonants, and the steadiness of vowels, can be made directly from the spectrogram. With VoceVista it is in addition possible to obtain a display of the power spectrum or the waveform signals from any point in a frozen spectrogram. All this information is retained in the memory of the computer and can be saved for further detailed analysis, for playback, or for instructional purposes such as matching a resonance pattern. A recommended application of the program would be to monitor continuously a lesson or a taped performance, occasionally freezing the current spectrogram display for closer investigation or future reference.

A final display is that of the envelope of the microphone signal. Although not calibrated, this gives a good indication of sound pressure level and thus the effectiveness of resonance strategies. Close examination of vibrato-related modulations in the audio envelope can often reveal precisely where a harmonic of the voice source is getting strong reinforcement from a formant of the vocal tract.

Spectrogram and Audio Envelope (VoceVista)