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Ultra-thin Acoustic Metasurface-Based Schroeder Diffuser
Yifan Zhu, Xudong Fan, Bin Liang, Jianchun Cheng, Yun Jing
TL;DR
The paper addresses the limited real-world maturity of acoustic metasurfaces by redesigning the Schroeder diffuser as an ultra-thin metasurface-based device. The resulting diffuser has performance comparable to the conventional design while being one order of magnitude thinner.
Problem
Acoustic metasurfaces remain at an embryonic stage for real-world applications, motivating a redesign of the established Schroeder diffuser.
Method
The paper revisits and redesigns the Schroeder diffuser using the concept of acoustic metasurface to create an ultra-thin metasurface-based diffuser.
Results
One order of magnitude thinner, the metasurface-based diffuser yields performance comparable to the conventional Schroeder diffuser.
Takeaways & Limitations
The metasurface-based design provides a thinner alternative with performance on a par with the conventional Schroeder diffuser.
Takeaways & Limitations
The diffuser has narrow bandwidth because of the unit cell’s resonance, and further schemes are needed to broaden its bandwidth.
Abstract
from arXiv · showhide
Schroeder diffuser is a classical design, proposed over 40 years ago, for artificially creating optimal and predictable sound diffuse reflection. It has been widely adopted in architectural acoustics and it has also shown substantial potential in noise control, ultrasound imaging, microparticle manipulation, among others. The conventional Schroeder diffuser, however, has a considerable thickness on the order of one wavelength, severely impeding its applications for low frequency sound. In this paper, a new class of ultra-thin and planar Schroeder diffusers are proposed based on the concept of acoustic metasurface. Both numerical and experimental results demonstrate satisfactory sound diffuse reflection produced from the metasurface-based Schroeder diffuser despite it being one order of magnitude thinner than the conventional one. The proposed design not only offer promising building blocks with great potential to profoundly impact architectural acoustics and related fields, but also constitutes a major step towards real-world applications of acoustic metasurfaces.
Figure Captions
The figures define the metasurface-based Schroeder diffuser, its broadband variant, and simulation–experiment comparisons against conventional Schroeder diffusers across incidence conditions and frequencies.
- Normal incidence: MSD figures compare simulated and measured three-dimensional scattering, acoustic pressure fields, directivity, and normalized diffusion coefficients for normal incidence.The comparisons include the MSD and a flat plane or plate, with frequency-dependent diffusion shown against the conventional SD.
- Oblique incidence: Oblique-incidence figures provide the corresponding simulated and measured scattering, field distributions, directivity, and normalized diffusion-coefficient comparisons.The oblique condition shown is 45° incidence.
- Broadband MSD: The BMSD design targets four frequencies using a quadratic residue sequence and relates reflected phase to the parameter w for four frequency components.BMSD1 and BMSD2 results mark targeted frequencies and compare simulated and measured diffusion at 0° and 45° incidence with the SD.