Sound Absorption and Diffusion by 2D Arrays of Helmholtz Resonators

Abstract

We report a theoretical and experimental study of an array of Helmholtz resonators optimized to achieve both efficient sound absorption and diffusion. The analysis starts with a simplified 1D model where the plane wave approximation is used to design an array of resonators showing perfect absorption for a targeted range of frequencies. The absorption is optimized by tuning the geometry of the resonators, i.e., by tuning the viscothermal losses of each element. Experiments with the 1D array were performed in an impedance tube. The designed system is extended to 2D by periodically replicating the 1D array. The 2D system has been numerically modeled and experimentally tested in an anechoic chamber. It preserves the absorption properties of the 1D system and introduces efficient diffusion at higher frequencies due to the joint effect of resonances and multiple scattering inside the discrete 2D structure. The combined effect of sound absorption at low frequencies and sound diffusion at higher frequencies, may play a relevant role in the design of noise reduction systems for different applications.

Prediction of acoustic wave transmission features of the multilayered plate constructions: A review

“…Dura et al. [183] considered an array of optimized HRs to analyze both effective acoustic absorption and diffusion. The procedure was followed to numerically analyze the 2D model and then examine it in an anechoic chamber based on measurement data.…”

Recent acoustic energy harvesting methods and mechanisms: A review

“…In the experiment by Herrero-Durá et al, 52 a new model of acoustic energy absorption is introduced with the help of five Helmholtz resonators which are made up of polylactic acid. In a tube, these series of different-sized five Helmholtz resonators (1D Array of HR), as shown in Figure 14, are placed to observe the behaviour of the floor of acoustic waves throughout the tube and the closest preamplifier microphones are mounted at 10 cm and 9 cm from the samples.…”

“…Figure 14. 1D Array of the Helmholtz resonator model, which is placed inside the tube of height Wt through which the source wave propagates and the rigid back plate of the same material used to obstruct the flow of the sound wave 52. …”

PT -symmetric Helmholtz resonator dipoles for sound directivity

“…In acoustics, asymmetric absorption has been demonstrated by detuned Helmholtz resonators (HRs) in one-dimensional waveguides [20]. More recently, one-and two-dimensional arrays of HRs were designed to achieve efficient sound absorption and diffusion [21]. Accordingly, a spatial distribution of HRs with modulated resonant frequencies and gain/loss can be feasible acoustic metamaterials, analogous to those in optics and microwave ranges.…”