Related Experiment Video
Updated: Dec 29, 2025
04:54
Author Spotlight: A Stable Phantom Material for Optical and Acoustic Imaging
Published on: June 16, 2023
3.6K
Reversed Doppler effect based on hybridized acoustic Mie resonances
Chen Liu1, Houyou Long1, Chen Zhou1
1Key Laboratory of Modern Acoustics, Department of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
Scientific Reports
|February 1, 2020
Summary
This study demonstrates a reversed Doppler effect in hybridized metamaterials (HM). These materials exhibit unusual sound wave behavior, including negative refraction and sound focusing, challenging previous acoustic limitations.
Area of Science:
- Acoustics
- Metamaterials
- Wave Physics
Background:
- Achieving reversed Doppler effects in double-negative acoustic metamaterials is a significant challenge.
- Understanding sound wave propagation in negative group velocity regimes is crucial for advanced acoustic applications.
Purpose of the Study:
- To demonstrate the reversed Doppler effect in a hybridized metamaterial (HM) system.
- To explore the acoustic properties of HM with double-negative parameters.
- To investigate sound wave focusing using a flat lens composed of HM.
Main Methods:
- Utilizing a simple Mie-resonator configuration to create the hybridized metamaterial.
- Analyzing the simultaneous double-negative acoustic parameters (effective dynamic bulk modulus and mass density) within overlapped frequency regions.
- Observing sound wave propagation and Doppler shift phenomena.
Main Results:
- Observed a reversed Doppler effect where approaching the source results in a redshift and receding results in a blueshift.
- Demonstrated negative phase velocity with reversed wavefronts and negative refraction within specific frequency ranges.
- Successfully realized sound wave focusing from a point source using a flat HM slab lens.
Conclusions:
- The hybridized metamaterial system effectively exhibits a reversed Doppler effect.
- The HM possesses unique acoustic properties, including negative refraction and the ability to focus sound waves.
- This research opens possibilities for novel acoustic devices and applications.
Related Concept Videos
01:05Doppler Effect - II
4.3K
The Doppler effect has several practical, real-world applications. For instance, meteorologists use Doppler radars to interpret weather events based on the Doppler effect. Typically, a transmitter emits radio waves at a specific frequency toward the sky from a weather station. The radio waves bounce off the clouds and precipitation and travel back to the weather station. The radio frequency of the waves reflected back to the station appears to decrease if the clouds or precipitation are moving...
4.3K
00:56Doppler Effect - I
5.9K
The Doppler effect and Doppler shift were named after the Austrian physicist and mathematician Christian Johann Doppler in 1842, who conducted experiments with both moving sources and moving observers. Consider an observer standing on a street corner, observing an ambulance with a siren sound passing by at a constant speed. The observer experiences two characteristic changes in the sound of the siren. Initially, the sound increases in loudness as the ambulance approaches and decreases in...
5.9K
01:12Double Resonance Techniques: Overview
628
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
628
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
1.4K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.4K
01:14Sound Waves: Resonance
3.1K
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...
3.1K
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
1.5K
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
1.5K