A pilot study on the influence of mouth configuration and torso on singing voice directivity

Directivity of speech and singing is determined primarily by the morphology of a person, i.e., head size, torso dimensions, posture, and vocal tract. Previous works have suggested from measurements that voice directivity in singing is controlled unintentionally by spectral emphasis in the range of 2-4 kHz. The attempt is made to try to identify to what extent voice directivity is affected by the mouth configuration and the torso. Therefore, simulations, together with measurements that investigate voice directivity in more detail, are presented. Simulations are presented for a piston in an infinite baffle, a radiating spherical cap, and an extended spherical cap model, taking into account transverse propagation modes. Measurements of a classical singer, an amateur singer, and a head and torso simulator are undertaken simultaneously in the horizontal and vertical planes. In order to assess differences of voice directivity common metrics, e.g., horizontal and vertical directivity indexes, are discussed and compared to improved alternatives. The measurements and simulations reveal that voice directivity in singing is affected if the mouth opening is changed significantly. The measurements show that the torso generates side lobes due to diffraction and reflections at frequencies related to the torso's dimensions.