Voice Source Differences Between Registers in Female Musical Theater Singers *†Eva Bjo ¨rkner, *Johan Sundberg, ‡Tom Cleveland, and ‡Ed Stone *Stockholm, Sweden, †Helsinki, Finland, and ‡Nashville, Tennessee Summary: Musical theater singing typically requires women to use two vocal registers. Our investigation considered voice source and subglottal pressure P s characteristics of the speech pressure signal recorded for a sequence of /pae/ syllables sung at constant pitch and decreasing vocal loudness in each register by seven female musical theater singers. Ten equally spaced P s values were selected, and the relationships between P s and several parameters were examined; closed-quotient (Q closed ), peak-to-peak pulse amplitude (U p-t-p ), am- plitude of the negative peak of the differentiated flow glottogram, ie, the maximum flow declination rate (MFDR), and the normalized amplitude quo- tient (NAQ) [U p-t-p /(T0*MFDR)], where T0 is the fundamental period. P s was typically slightly higher in chest than in head register. As P s influences the measured glottogram parameters, these were also compared at an approxi- mately identical P s of 11 cm H 2 O. Results showed that for typical tokens, MFDR and Q closed were significantly greater, whereas U p-t-p and therefore NAQ were significantly lower in chest than in head. Key Words: Voice source—Subglottal pressure—Flow glottogram—Normalized amplitude quotient—Female singers—Musical theater singing. Accepted for publication January 25, 2005. Presented at the 18th International Congress on Acoustics: ICA 2004, Kyoto, Japan, April 5, 2004. From the *Department of Speech Music Hearing, KTH, Stockholm, Sweden; †Laboratory of Acoustics and Audio Signal Processing, Helsinki University of Technology, Helsinki, Finland; and ‡Vanderbilt VoiceCenter, Dept.of Otolaryngology, Vanderbilt University Medical Center, Nashville, Tennessee. The work of E. B. is supported by the European Community’s Human Potential Programme under Contract HPRN-CT-2002- 00276 [HOARSE-network]. Address correspondence and reprint requests to Eva Bjo ¨rkner, Laboratory of Acoustics and Audio Signal Processing, Helsinki University of Technology, PO Box 3000, FIN-02015 HUT Finland. E-mail: evab@speech.kth.se Journal of Voice, Vol. 20, No. 2, pp. 187–197 0892-1997/$32.00  2006 The Voice Foundation doi:10.1016/j.jvoice.2005.01.008 187 INTRODUCTION Vocal register is a phenomenon of great relevance in vocal art, particularly in female singing. The aim of this study was to explore and deepen the knowl- edge about the voice source characteristics in the female singing voice. Results from seven singers are presented, and the recently introduced normal- ized amplitude quotient (NAQ) parameter serves as a complementary measurement. According to Titze, 1 “the term register has been used to describe perceptually distinct regions of vocal quality that can be maintained over some ranges of pitch and loudness.” The register used by female singers in the lower part of their pitch range is generally referred to as chest or modal and the register in the adjacent higher part as head, middle, or falsetto, henceforth chest and head register, respectively. An important task in singing training,