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Acoustic Characteristics of Voice in Music and Straight Theatre
Towards a Systematic Empirical Foundation


Stage voices feature special qualities when it comes to vocal range, efficiency, dynamic range and projection. Acoustically, these qualities are described as properties of language-specific (lower formants) and style-specific (higher formants) attributes of vocal sound.–With regard to vocal training in music and straight theatre, however, the question rises as to the reliability and the utilization of acoustic evidence as given hitherto.


Acoustic properties of trained voices in music and straight theatre: In comparison to non-trained voices, stage voices generally feature greater efficiency, projection and dynamic range. In singing, this is closely connected with style-specific strategies to balance vowel timbre and adjust articulation on higher fundamental frequencies in order to obtain a homogenous voice timbre and maintain the efficiency of vocal performance.–In the existing literature, these training and style-specific properties are commonly related to three spectral phenomena: Adjustment of vocal tract resonances to frequencies of partials (harmonics), in particular for mid and high-range fundamental frequencies ("resonance/formant tuning"), increased intensity of mid and high-range frequencies, and a distinct peak of a relative energy maximum at 2.5 to 3kHz for singing ("singer’s formant") and approximately 3.5 kHz for stage acting ("actor’s formant").

Questions regarding vocal training: Taking into consideration the latest techniques of digitization and real-time spectral visualization, we are faced with two questions for vocal training: How reliable is modern training and style-specific acoustic evidence as given in the literature? What kind of insight does this generate for vocal training and what kind of specific applications can be extrapolated? The present project attempts to tackle the first question.

Project–approach: Currently, there is no systematic and reliable empirical approach that allows for a straightforward understanding, tracking and visualization of acoustic qualities of stage voices. In particular, there is a lack of systematic studies of vowels on varying pitch (with a range of up to two octaves) that enable a direct comparison of voice and production qualities of singers ("legit" and "belt"), actresses/actors and untrained voices, including a variation of additional basic production parameters. Moreover, with regard to pronounced variation in fundamental frequency, methodological questions of how to analyze the acoustic properties of voiced sounds still remain open.

The present project addresses this gap. In the framework presented, with regard to Standard German, a systematic empirical basis is being laid regarding the acoustic characteristics of trained voices in music and straight theatre as well as differences in comparison with untrained voices. Furthermore, it provides an assessment regarding the aptitude of existing approaches for acoustic analyses of vocal productions of stage voices.

Project–recordings and recognition: Trained female and male singers and actresses/actors as well as untrained adults and children are asked to produce the German vowels /iː, yː, eː, øː, ɛː, aː, oː, uː/ (V and sVs) with varying production parameters (pitch, vocal effort, style, phonation type, including whispering, creaky voice, shouting). In addition, they are asked to read out loud a text passage (phonetically balanced) and sing a short passage. As a reference group for “average” conversational speech, 30 untrained speakers will also be asked to read the text and sing the passage mentioned.–All utterances will be recorded and edited.–All recordings of V and sVs type vowels will be tested in recognition (vowel discrimination) tests.

Project–acoustic analysis: The aptitude of various approaches to acoustic analyses is being assessed on the bases of the recordings mentioned above. According to the results of this assessment, the recordings will be analytically investigated and statistically exploited for training and style-specific acoustic characteristics.

Project–results: The results aimed at are: (1) A comprehensive systematical database of vocal productions by trained singers ("legit" and "belt") and actresses/actors as well as by untrained speakers, as empirical basis and reference. (2) Determining the method of acoustic analysis of voiced sounds suitable to describe a variation of production parameters typical for stage voices. (3) Determining training and style-specific acoustic voice characteristics that can be tracked and visualized in a straightforward manner.

Publications of journal papers are intended and the database will be made available in an adequate format for the use in vocal training and research.

Aesthetics of the voice: The present project contributes to the interdisciplinary research on the aesthetics of the voice.

Keywords: voice, speech, singing, acting, vowel, fundamental frequency, vocal effort, formant, formant tuning,  singer’s formant cluster, speaker's/actor’s formant cluster, scoustic phonetics, speech perception

Project Duration

1/3/2013 to 31/5/2015

Teams and Affiliations

Zurich University of the Arts (ZHdK), Institute for the Performing Arts and Film (IPF):

Dieter Maurer, Prof. Dr., head of project
Christian d’Heureuse, research associate
Heidy Suter, MA, research associate
Lina Maria Åkerlund, Prof., singer, research associate
Martina Bovet, Prof., singer, research associate
Markus Eiche, dipl Ing., singer, research associate
Fraziska Feucht, dipl. sound editor, research associate
Rahel Hadorn, Prof., singer, research associate
Oliver Mannel, dipl. voice and speech teacher, designated Linklater voice teacher,
research associate

University of Zurich, Phonetic Laboratory:

Volker Dellwo, Prof. Dr., co-head of project
Daniel Friedrichs, MA, research assistant and PhD student

Cooperation with External Schools, Theatres and Research Groups

Opernhaus Zurich, Christian Venghaus, head of sound department
Otto Falckenberg Schule, Fachakademie für Darstellende Kunst, Munich, Andreas Sippel
University College London UCL, Speech, Hearing & Phonetic Sciences, Dr. Mark Huckvale, Prof. Dr. Stuart Rosen

Internal Cooperation at the Zurich University of the Arts

Department of Performing Arts and Film, Department of Music, Res Bosshart, head MA Theatre, head MA Opera,
Department of Music, Prof. Hans Peter Künzle, head MA Jazz Department of Music, Prof. Heiko Freund, head MA Pop


Swiss National Science Foundation SNSF, grant no. 100016_143943