Thermally Programmable Two-Port Non-Hermitian Acoustic Metastructure for Broadband and Direction-Dependent...

Area of Science:

• Acoustics
• Materials Science
• Metamaterials

Background:

• Metamaterials offer unique acoustic properties not found in natural materials.
• Controlling acoustic properties, especially absorption, is crucial for noise reduction and acoustic device design.
• Tunable acoustic devices are desirable for adaptive sound control applications.

Purpose of the Study:

• To propose and model a thermally programmable two-port non-Hermitian acoustic metastructure.
• To achieve broadband and direction-dependent sound absorption using temperature as a tuning parameter.
• To investigate the mechanism of thermally programmable asymmetric absorption.

Main Methods:

• Utilized a unified transfer-matrix and electro-acoustic circuit modeling framework.
• Quantitatively described the influence of thermal variations on air properties (density, viscosity, speed of sound).
• Performed numerical analyses to evaluate absorption bandwidth and reflection suppression.

Main Results:

• Demonstrated broadband (321 Hz) and direction-dependent sound absorption at a subwavelength scale.
• Showcased asymmetric absorption linked to exceptional point behavior via thermal modulation.
• Achieved programmable control of non-Hermitian coupling through temperature changes without geometric modification.

Conclusions:

• The proposed framework clarifies the mechanism of thermally programmable asymmetric absorption.
• The study provides a compact route for broadband sound control in variable-temperature environments.
• Offers fundamental guidance for designing programmable acoustic absorbers for diverse applications.