Acoustic Coherent Perfect Absorbers as Sensitive Null Detectors

Area of Science:

• Acoustics
• Wave Phenomena
• Materials Science

Background:

• Coherent perfect absorption (CPA) is a phenomenon where incident waves are completely absorbed by a system.
• Achieving CPA typically requires specific structural and wave conditions.
• Previous studies have explored CPA in various wave domains, but experimental realization with diverse scatterers remains an active area of research.

Purpose of the Study:

• To experimentally demonstrate acoustic coherent perfect absorption (CPA) using four distinct symmetric scatterers.
• To investigate the conditions necessary for CPA in these scatterers, focusing on reflection/transmission amplitudes and incident wave properties.
• To explore the potential of these CPA systems as sensitive detectors for subtle changes in incident wave parameters.

Main Methods:

• Experimental setup involving four symmetric scatterers with different structures.
• Precise control of two collinear and counter-propagating incident acoustic waves, including their relative amplitude and phase.
• Measurement of output power modulation by varying the relative phase of incident waves.
• Assessment of scatterer sensitivity to phase deviations from optimal CPA conditions.

Main Results:

• Successful experimental realization of acoustic CPA for all four symmetric scatterers.
• Demonstrated nearly 1000-fold modulation of output power by adjusting the incident wave phase over 180°.
• Showcased the potential of these scatterers as sensitive devices for detecting small differences between incident waves.
• Quantified a 27% change in scattering wave strength for every degree of phase deviation from the optimal CPA condition.

Conclusions:

• Acoustic CPA is achievable with diverse symmetric scatterers under specific wave conditions.
• The demonstrated output power modulation highlights the practical potential of CPA systems.
• These CPA systems exhibit high sensitivity to phase variations, paving the way for novel sensing applications in acoustics.