Recent Advances in Active Acoustic Metamaterials

Since its first demonstration of an acoustic metamaterial in the early 21st century, it is widely used for sound wave manipulation purposes in many applications such as aerospace, automotive, defense, marine, etc. However, the traditional acoustic metamaterials display acoustic characteristics for restricted use because of their fixed structures. For real-world applications, the active sound wave manipulation is desirable. In recent years, active acoustic metamaterials (AAMs) have garnered attention owing to their unique design and material characteristics, which result in various dynamic responses against the incoming sound wave. This paper aims to provide an overview of the fundamental concept of active metamaterials, describing the multiple tuning mechanisms and design strategies, and highlighting their potential applications. The current fabrication challenges and future outlook in this promising field are also discussed.