INTERNATIONAL CONGRESS ON ACOUSTICS MADRID , 2-7 SEPTEMBER 2007 DIRECTIVITY MEASUREMENTS OF THE SINGING VOICE PACS : 43

This work presents initial results of a detailed measurement study on singing voice directivity under various conditions in twoand three-dimensions. Unlike previous studies that have used average directivity data over sung phrases or crescendos, this work presents results that are measured and analyzed in finer detail. A professional opera singer (counter tenor) participated in the experiments. Measurements are based on simultaneous recording using an array of 24 microphones mounted on a movable semi-circular arch in an anechoic room. Video recordings serve for estimation of the mouth shape and opening. Details of the measurement protocol and post-treatment processing are presented. Specifically, the variations in directivity relative to pitch, level (piano, fortissimo, etc.), vowel, and controlled “voice projection” by the singer have been investigated. The application of directivity patterns to radiating sources in computer simulations and auralizations is common for loudspeaker models. Few applications include the directivity patterns of natural sources, partly due to the lack of sufficient data. Results of this work are applicable to vocal production research, simulator design, room acoustic sound field prediction, and virtual reality systems with musical applications. INTRODUCTION While there have been numerous studies concerned with the directivity of musical instruments, there have been very few studies concerned with the directivity of the human voice. Human directivity measurements for 66 spatial positions and 13 frequency bands have been reported in the pioneering work of Dunn and Farnsworth [1] using one speaker repeating 15s of speech. The results show a greater variation in directivity patterns at higher frequencies. Directivity variations linked to the size of the mouth opening occurred above 5600 Hz. Flaganan [2] proposed new measurements with a calibrated artificial sound source in a mannequin. He also compared the results obtained with simple analytic models: piston in a sphere, baffled piston. Using an array of microphones mounted on a double arc Chu and Warnock [3] showed that similar directivities were obtained for both normal and loud voice levels but significant changes behind the talker were observed for low voice level. No significant differences in directivity were detected between male and female talkers although male and female voices had different spectra. An effect of the aperture size of the mouth has been studied [4]. Open and close vowels give different patterns above about 1000 Hz. This seemed in agreement with an analytic model of a piston (corresponding to mouth aperture) radiating on a sphere (with corresponding head radius). Finally, Kob and Jers [5,6] compared radiation patterns for an artificial singer head and real singers, showing comparable results for sustained vowels. MOTIVATION OF THE WORK In the present work, we investigate several aspects of radiation patterns in singing. A first question is the difference between loud voice and soft voice, as discussed by Chu and Warnock [3]. A second question is the effect of the sung vowel as discussed by Halkosaari, Vaalgamaa, and Karjalainen [4]. A more challenging question arose from discussions with professional singers who are often called to sing in large rooms. In voice pedagogy, many singers are using the metaphor of voice “projection” or voice “focusing”. This terminology seems to imply some sort of spatial effect or voice directionality control. A matter of serious interest with regards to directivity this metaphor is only a matter of singer’s perception or whether it resulted in actual changes in voice radiation patterns. These conditions are studies using sustained vowel singing and 1/3-octave band analysis. This provides detailed results for these various conditions which has not previously been presented.