RESUMO
A time-domain sound field reproduction (SFR) method based on the group Lasso (GL) is presented. The proposed method optimizes the positions and the number of active loudspeakers in the time domain by iteratively solving a mixed-norm constrained optimization problem. Simulation results demonstrate that the proposed method achieves accurate broadband SFR using a small number of active loudspeakers and significantly outperforms the least-squares method when the desired sound field is under-sampled. Moreover, the GL algorithm can also be used to optimize the loudspeaker placement for sound field control systems.
RESUMO
Two types of block sparse models are presented to interpolate the early part of the acoustic transfer functions (eATFs) between the loudspeakers and the target spatial regions in reverberant rooms. The desired eATFs are modeled as a superposition of sound fields generated by a dense grid of equivalent point sources, which exhibit two kinds of block sparse structures under the far-field and small target region assumptions. Simulation results in the two-dimensional case demonstrate that the proposed models can provide accurate eATF interpolation over a broad frequency range using a small number of microphones.
RESUMO
Acoustic attenuation performance through a constricted duct is greatly improved by an annular resonator. A method based on the Green's function for a semi-infinite circular duct is proposed to calculate the transmission loss, where the velocity distributions are assumed to be uniform at the constriction inlet/outlets and at the inlet to the annular resonator. From an analogous acoustical circuit, the effect of higher order evanescent modes on the quarter-wave resonance is described by an extra length. The improved acoustic attenuation performance is also confirmed by an experiment.
