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/. 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