Conference_programme: 19.1 - Duct Acoustics
Lecture: A study of sound propagation in ducts with a moving boundary wall
Author(s): Dang Jianwu, Hou Qingzhi, Wang Futang
Summary:
Duct acoustics usually deals with the duct with a hard-wall or soft-wall. When a duct has a moving wall such as the vocal tract whose configuration changes with time, how does the acoustic characteristics of sound propagation are affected by the moving boundary of the duct. In this study, we combine the finite-difference time-domain (FDTD) with the immersed boundary method (IBM) to investigate the sound propagation in the ducts with a moving boundary. To replicate the property of a free space by a finite computational field, eight layers of the perfect matching layer (PML) were set around the computational field (CF) to absorb the outgoing waves. FDTD of the hybrid method discretizes the whole CF by a Cartesian grid (Eulerian points), where the duct is immersed in the relatively larger CF, and IBM uses a series of discrete control points (Lagrangian points) to replicate the geometrical wall, and to block out the inner grids by the Lagrangian force. When the wall moves, the Lagrangian points will travel in the CF. Numerical experiments were carried on uniform ducts, convergent and divergent ducts. As the results, sound pressure distribution demonstrated the physical properties of the ducts under a variety of conditions. The resonant frequencies of the ducts show the reasonable accuracy, whose error is within 10% comparing with the theoretical value.
Corresponding author
Name: Prof Jianwu Dang
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Country: Japan
