Flow vibrato in singers

Abstract

Frequency (F0) vibrato is commonly known, but not so for flow vibrato, the mean flow variation that accompanies frequency vibrato. Two classically trained singers, each with over 20 years professional experience, a soprano and a tenor, recorded /pa:pa:pa:/ sequences on three pitches (C4, A4, and G5 for the soprano, D3, D4, and G4 for the tenor) and three loudness levels (p, mf, and f) at each pitch. Each vowel had 3–6 frequency vibrato cycles. For both singers, flow vibrato (obtained using the Glottal Enterprises aerodynamic system) was present, and the lowest pitch had the most variability; otherwise, flow vibrato was fairly sinusoidal in shape. For the soprano, flow vibrato cycle extents were: 21–88 cc/s, lowest pitch; 60–147 cc/s, middle pitch; 115–214 cc/s, highest pitch, across loudness levels. For the soprano, the phase difference for the flow was 120–180 degrees ahead of the F0 vibrato. For the tenor, the flow vibrato cycle extents were: 32–85 cc/s, lowest pitch; 98–113 cc/s, middle pitch; 76–240 cc/s, highest pitch, across loudness levels. Flow vibrato for the tenor led the F0 vibrato typically by 40–120 degrees. For both subjects, some flow vibrato cycles had double peaks. Flow vibrato needs further study to determine its origin, shapes, and magnitudes.