2019 Volume 40 Issue 5 Pages 325-335
This paper presents an expanded theory for relating airborne-sound-excited and force-excited sound radiations from solid structures. Although the reduction of these two types of sound radiation is a fundamental issue in noise-control engineering, each of them has been historically treated as a separate issue. The reduction in the former is normally called airborne sound insulation and separated from the latter, especially in architectural acoustics. A previous study (M. Yairi et al., J. Acoust. Soc. Am., 140, 453–460 (2016)) established a fundamental relationship between the sound radiations from random-incidence sound-excited and point-force-excited vibrations of a single-leaf infinite elastic plate. A conversion function that relates the two excitation cases was presented in a simple closed form, not including the parameters of the plates, which included of only the specific impedance and the acoustic wavenumber of the medium surrounding the plate. In this paper, the applicability of the conversion function is expanded from a single-leaf infinite elastic plate model to a double-leaf infinite elastic plate model. The sound radiation from a double-leaf infinite elastic plate driven by random-incidence sound and that driven by point-force excitation are theoretically investigated. The conversion function derived from the present model successfully relates the two excitation problems at all analyzed frequencies and has been shown to agree with the previously established single-leaf theory.
