Electroacoustic material for optimal apparent sound absorption

Conventional porous materials are ineffective at absorbing low-frequency sounds, while acoustic resonators typically provide sound absorption within a narrow frequency band. These limitations present a significant challenge for controlling noise in various applications. This work investigates the acoustic properties of an active electro-mechano-acoustic material capable of broadband sound absorption. Previous works have relied on sensors and digital signal processing to externally control the material's sound absorption. Here, we develop an analytical electro-mechano-acoustic model of a system comprising a non-ideal sound source within an impedance tube and the active material. This model not only provides insights into the system's underlying physics but also yields an expression for the material's apparent reflection coefficient, thereby linking the acoustic, mechanical, and electrical parameters of the system components with the acoustic behaviour of the electroacoustic absorber. Using this expression, we derive the optimal input voltage characteristics required to control sound absorption without relying on wave sensing, external signal processing, or controllers. Theoretical predictions are successfully validated through numerical and experimental data. This work has potential applications in active acoustic treatments and tunable acoustic metamaterials for wave control.