Numerical model research for the sound energy conversion in air-modulated speaker

作者：Zhao Yun^*; Zeng Xinwu

来源：Acta Acustica, 2011, 36(3): 291-300.

• Acoustic analogy
• Acoustic signals
• Analysis tools
• Chamber pressure
• Conversion process
• Dynamic mesh
• Dynamic mesh technique
• Engineering design
• Free shear layer
• Frequency dependence
• Harmonic components
• High frequency
• Hybrid computational
• Internal flows
• Low-frequency case
• Near-field acoustics
• Near-wall
• Non-Linearity
• Numerical models
• Predominant frequency
• Primary parameters
• Quadrupoles
• Quasi-steady theory
• Radiation field
• Shear-stress transport
• Sound energy
• Unsteady reynolds-averaged navier-stokes
• Vocal-tracts
• Voice coil
• Wall treatment
• Williams
• Working conditions

The numerical model of air-modulated speaker (AMS) based on the hybrid computational aero-acoustics (CAA) method is proposed to overcome quasi-steady theory limitation in high frequency and low chamber pressure conditions and provide analysis tool to relate engineering designs with characteristics in radiation field. Characteristics in both fields at typical working condition are analyzed. Frequency dependence in energy conversion process is emphasized. The internal flow of AMS is described by unsteady Reynolds-averaged Navier-Stokes (RANS) equation, shear-stress transport (SST) k-ω turbulence model is coupled with enhanced wall treatment to predict flow separation in the vocal tract, the dynamic mesh technique is utilized for modeling of voice coil modulation, and porous Ffowcs Williams and Hawkings (FW-H) integral is used for near field acoustic calculation. Primary parameters are properly selected in compressible flow, dynamic mesh, near-wall mesh generation, boundary condition, and acoustic analogy to make unsteady flow and acoustic field accurate. Agreement in steady flow is obtained between simulation and experiment results. Predominant frequency in acoustic signal is basically consistent with modulated function, and harmonic components due to nonlinearity are evident. Compared to the low frequency case, vortex evolution and free shear layer presence make dipole and quadrupole sources unable to be neglected in corresponding acoustic field prediction.

• 出版日期2011