8 VOCE VISTA, ELECTROGLOTTOGRAMS, CLOSED QUOTIENTS Donald G. Miller , Resonance in Singing, (Chapters 2, 5)

VOCE VISTA VOCE VISTA IS A PROGRAM FOR ANALYZING AND DISPLAYING SOUNDS, ESPECIALLY EFFECTIVE FOR MUSICAL SOUNDS VOCE VISTA CAN SIMULTANEOUSLY DISPLAY THE WAVEFORM ENVELOPE, THE SPECTROGRAM, AND THE SOUND SPECTRUM

Spectrogram of soprano octave scale to B5-flat with power spectrum at F5. Cursor at 4168 Hz marks second harmonic of F5 at 1385 Hz. The level of that harmonic is measured at -15 dB (from Miller 2008)

ELECTROGLOTTOGRAPH (EEG) THE ELECTROGLOTTOGRAPH IS A PHYSIOLOGICAL SIGNAL THAT INDICATES THE OPENING AND CLOSING OF THE GLOTTIS. IT IS OBTAINED BY HOLDING TWO ELECTRODES TO THE NECK ON EITHER SIDE OF THE LARYNX SO THAT A SMALL CURRENT RUNS BETWEEN THEM. The resistance between the electrodes decreases by a small amount when the vocal folds make contact, initiating the closed phase of the glottis. IN SINGING, THE CLOSING OF THE GLOTTIS IS TYPICALLY QUITE ABRUPT AND IS USUALLY EASY TO IDENTIFY THROUGH A SHARP RISE IN THE EEG SIGNAL.

Spectrogram of tenor octave scale to A4-flat, vowel /a/ Spectrogram of tenor octave scale to A4-flat, vowel /a/. Waveform display shows 9 ms detail of the spectrogram at the cursor, placed at G4 (5650 ms). Delay of audio signal is determined as 1.5 ms. On the EEG signal, the horizontal cursor is placed at estimated glottal opening. F0 (392 Hz) and closed quotient (79%) are calculated and displayed.

CLOSED QUOTIENT THE CLOSED QUOTIENT IS THE PERCENTAGE OF THE GLOTTAL PERIOD IN WHICH THE GLOTTIS IS CLOSED. THE EEG PANEL IS FURNISHED WITH ONE HORIZONTAL AND THREE VERTICAL CURSORS. THE USER ADJUSTS THE HORIZONTAL CURSOR TO INTERSECT THE EGG SIGNAL AT THE ESTIMATED POINT OF GLOTTAL OPENING. THE MIDDLE VERTICAL CURSOR THEN INTERSECTS THE EGG SIGNAL AT THIS SAME POINT. VOCE VISTA ESTIMATES THE CLOSED QUOTIENT FROM THE EEG WAVEFORM

SIGNIFICANCE OF CLOSED QUOTIENT A LARGE CQ ENABLES INCREASEDD GLOTTAL RESISTANCE, ALLOWINGTHE SINGER TO BUILLD HIGHER SUBGLOTTAL PRESSURE AND WITH IT, A HIGHER SOUND PRESSURE LEVEL THE VOCAL TRACT WITH THE GLOTTIS CLOSED IS A BETTER RESONATOR THAN WITH IT OPEN. A LARGER CQ INCREASES THE RESONANCE A LARGE CQ BOOSTS THE HIGHER FREQUENCY COMPONENTS OF THE SOUND OUTPUT IN THE OF THE VOCAL TRACT IN THE RANGE OF THE SINGER’S FORMANT

LARGE CLOSED QUOTIENT Spectrum and waveform of a bass vowel /E/. The strong B4 resonated by the second formant, creates a strong fourth maximum in the audio and the glottal opening is delayed up to that maximum