Topology-Optimized Omnidirectional Broadband Acoustic Ventilation Barrier

As a problem in acoustics, sound insulation finds wide applications in diverse situations. We design and experimentally implement an omnidirectional broadband acoustic ventilation barrier using a topology-optimization method. We propose a broadband acoustic barrier constructed of interlaced contraction structure with a central hollow channel, utilizing Bragg’s scattering mechanism happening at impedance discontinuities. Based on this barrier, a density-based topology-optimization method is employed for the inverse design to broaden the sound-insulation band nearly 90% while keeping a low transmission. The topology-optimization method systematically optimizes the scatterers distributed at intervals in our initial barrier in dimensions of size, shape, and orientation to possess many complicated features, which produces the maximum reflection at a desired frequency range. Experiments with acoustic waves of different incident angles are conducted to validate the optimized design, whose results are consistent with the simulations. The measured ventilation rate of the optimized barrier reaches 60.8% compared to initial barrier (49.2%) due to the reduction of fill rate of solid material and aerodynamic loss, demonstrating a high ventilation effect. Our design opens routes to design sound insulators that enable applications to be air permeable yet sound proofing simultaneously.

Figure 1

(a) Schematic diagram of unit cell of the two-dimensional periodic interlaced contraction structure. (b) The band structure of the two-dimensional periodic interlaced contraction structure.

Figure 2

(a) Schematic illustration for the initial broadband acoustic barrier. (b) Fixed design domain and boundary conditions. The design unit of the initial acoustic barrier is indicated by the large rectangular box (bold line).

Figure 3

(a) Frequency dependences of sound-pressure amplitude transmission for initial barrier and optimized barriers. (b) Interpolation function of Eq. (3). (c) Schematic illustration for the optimized broadband acoustic barrier. The unit of the optimized structure is indicated by the rectangular box (bold line). (d)–(g) Sound-pressure fields of initial barrier and optimized barriers at 3690 and 6930 Hz.

Figure 4

(a)–(c) Frequency dependences of sound-pressure amplitude transmission for initial barrier and optimized barriers for three incident angles: θ = 30°, 60°, and 85°. (d) Spatial distribution of acoustic pressure when the proposed acoustic barrier is impinged by a point source driven by the frequency of 5500 Hz.

Figure 5

(a) Schematic illustration of the experimental setup. (b) The top and front view photography of the sample fabricated by 3D printing technique. (c), (d) Measured and simulated frequency dependences of sound-pressure amplitude transmission for the optimized acoustic barrier for four incident angles: θ = 0°, 30°, 60°, and 85°.