Related Experiment Video
Updated: May 2, 2026
09:39
Characterizing Dissipative Elastic Metamaterials Produced by Additive Manufacturing
Published on: June 28, 2024
1.9K
Non-reciprocal and highly nonlinear active acoustic metamaterials
Bogdan-Ioan Popa1, Steven A Cummer1
1Department of Electrical and Computer Engineering, Duke University, PO Box 90291, Durham, North Carolina 27708, USA.
Nature Communications
|February 28, 2014
Summary
Researchers developed subwavelength acoustic devices using metamaterial techniques. These novel unidirectional sound devices offer high performance for audio and low frequencies.
Area of Science:
- Acoustics
- Metamaterials
- Nonlinear acoustics
Background:
- Unidirectional acoustic devices are crucial for many applications.
- Existing subwavelength devices struggle with time-reversal symmetry breaking at audio frequencies.
Purpose of the Study:
- To present a design approach for highly subwavelength and non-reciprocal acoustic devices.
- To demonstrate a practical implementation using metamaterial techniques.
Main Methods:
- Designed a unit cell using a piezoelectric membrane, nonlinear electronic circuit, and Helmholtz cavities.
- Experimentally characterized the acoustic performance of the designed device.
Main Results:
- Achieved a highly subwavelength device (thinner than 1/10th of a wavelength).
- Demonstrated a strong isolation factor of over 10 dB.
- The design method supports broadband unidirectional devices.
Conclusions:
- Metamaterial-based techniques enable the creation of effective subwavelength unidirectional acoustic devices.
- The proposed design is a promising candidate for various acoustic applications requiring non-reciprocity.
Related Concept Videos
01:25Active Filters
1.4K
Active filters are electronic circuits that use operational amplifiers (op-amps), resistors, and capacitors to filter out unwanted frequency components from a signal. A first-order low-pass active filter is designed to pass signals with a frequency lower than a certain cutoff frequency and attenuate frequencies higher than that cutoff frequency. The transfer function for a first-order low-pass active filter is:
1.4K
00:53Sound Waves: Interference
4.2K
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...
4.2K
01:14Sound Waves: Resonance
2.8K
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...
2.8K
01:27Passive Filters
1.2K
Passive filters are utilized to shape the frequency spectrum of signals across a diverse array of applications. These filters, using only passive elements like resistors (R), inductors (L), and capacitors (C), are capable of selectively allowing or blocking certain frequency ranges without the need for external power sources.
Low-Pass Filters
Low-pass filters are designed to transmit signals with frequencies lower than the cutoff frequency, ωc, and attenuate those above it. The cutoff...
Low-Pass Filters
Low-pass filters are designed to transmit signals with frequencies lower than the cutoff frequency, ωc, and attenuate those above it. The cutoff...
1.2K
01:10Interference: Path Lengths
2.5K
Consider two sources of sound, that may or may not be in phase, emitting waves at a single frequency, and consider the frequencies to be the same.
Two special sources may be considered when they are in phase. This can be easily achieved by feeding the two sources from the same source. An example would be synchronizing the two speakers by feeding them with the same source, such as the sound waves produced by a tuning fork. This setup ensures that the two sources have the same frequency and are...
Two special sources may be considered when they are in phase. This can be easily achieved by feeding the two sources from the same source. An example would be synchronizing the two speakers by feeding them with the same source, such as the sound waves produced by a tuning fork. This setup ensures that the two sources have the same frequency and are...
2.5K
01:28Standing Waves in a Cavity
1.7K
A household microwave and lasers are examples of standing electromagnetic waves in a cavity. When two conducting metal plates are placed parallel at the nodal planes, it creates a cavity where standing waves are formed. The cavity between the two planes is analogous to a stretched string held at the points x = 0 and x = L. Here, the distance 'L' between the two planes must be an integer multiple of half of the wavelength. The wavelengths that satisfy this condition are given by:
1.7K