Related Experiment Video
Updated: Feb 7, 2026
07:38
Characterization of Biological Absorption Spectra Spanning the Visible to the Short-Wave Infrared
Published on: January 10, 2025
3.2K
Tunable Sound Absorption via Evanescent-Wave Coupling in Asymmetric Bilayer Metasurfaces
1Department of Mechanical Engineering, Gachon University, Seongnam, Republic of Korea.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|February 6, 2026
Summary
This study presents tunable sound absorption using bilayer acoustic metasurfaces. Adjusting cavity length controls sound reflection and absorption, offering dynamic noise control solutions.
Area of Science:
- Acoustics
- Materials Science
- Wave Physics
Background:
- Acoustic metasurfaces offer unique sound manipulation capabilities.
- Controlling sound absorption dynamically remains a challenge for practical applications.
Purpose of the Study:
- To explore tunable sound absorption using a bilayer configuration of phase-gradient acoustic metasurfaces.
- To demonstrate broadband tunability in sound absorption by adjusting the cavity length between metasurface layers.
Main Methods:
- Developed an analytical model based on coupled-mode theory to analyze scattering behavior.
- Utilized full-wave simulations with bilayer metasurfaces realized with space-coiling structures.
- Investigated evanescent-wave coupling influenced by phase gradient and integer parity.
Main Results:
- Achieved modulation between highly reflective and perfectly absorptive states by adjusting cavity length.
- Demonstrated broadband tunability in sound absorption, with absorption coefficients exceeding 95%.
- Validated theoretical predictions with simulation results.
Conclusions:
- The proposed bilayer metasurface system offers effective dynamic sound control.
- Structural simplicity and high tunability make it suitable for noise barriers and sound-absorbing devices.
Related Concept Videos
01:35Asymmetric Lipid Bilayer
9.9K
Biological membranes show uneven distribution of different types of lipids in the inner and outer layers, resulting in transverse asymmetric membranes. The treatment of the erythrocyte membrane with the enzyme phospholipase confirmed the asymmetric nature of the lipid bilayer. The enzyme hydrolyzes lipids into fatty acids and hydrophilic groups. The phospholipase acts only on the outer layer of the membrane, while the inner layer remains intact. The phospholipase treatment resulted in 80%...
9.9K
01:01Sound Waves
13.0K
Sound waves can be thought of as fluctuations in the pressure of a medium through which they propagate. Since the pressure also makes the medium's particles vibrate along its direction of motion, the waves can be modeled as the displacement of the medium's particles from their mean position.
Sound waves are longitudinal in most fluids because fluids cannot sustain any lateral pressure. In solids, however, shear forces help in propagating the disturbance in the lateral direction as well....
Sound waves are longitudinal in most fluids because fluids cannot sustain any lateral pressure. In solids, however, shear forces help in propagating the disturbance in the lateral direction as well....
13.0K
01:14Sound Waves: Resonance
3.4K
Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical boundary conditions (i.e., has a node at each end). A node is defined as a fixed point where the string does not move. The symmetrical boundary conditions result in some frequencies resonating and producing standing waves, while other frequencies interfere destructively. Sound waves can resonate in a hollow tube, and the frequencies of the sound...
3.4K
01:17Sound as Pressure Waves
4.5K
Sound waves, which are longitudinal waves, can be modeled as the displacement amplitude varying as a function of the spatial and temporal coordinates. As a column of the medium is displaced, its successive columns are also displaced. As the successive displacements differ relatively, a pressure difference with the surrounding pressure is created. The gauge pressure varies across the medium.
The pressure fluctuation depends on the difference in displacements between the successive points in the...
The pressure fluctuation depends on the difference in displacements between the successive points in the...
4.5K
01:01Perception of Sound Waves
5.7K
The human ear is not equally sensitive to all frequencies in the audible range. It may perceive sound waves with the same pressure but different frequencies as having different loudness. Moreover, the perception of sound waves depends on the health of an individual's ears, which decays with age. The health of one's ears may also be affected by regular exposure to loud noises.
The pitch of a sound depends on the frequency and the pressure amplitude of the source. Two sounds of the same...
The pitch of a sound depends on the frequency and the pressure amplitude of the source. Two sounds of the same...
5.7K
00:53Sound Waves: Interference
4.8K
Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure waves. When two identical waves from the same source superimpose on each other, the combination of two crests or two troughs results in amplitude reinforcement known as constructive interference. If two identical waves, that are initially in phase, become out of phase because of different path lengths, the combination of crests with troughs...
4.8K