In a groundbreaking development, researchers have successfully demonstrated the phenomenon of non-Hermitian tunneling in the realm of acoustics, paving the way for innovative applications in sound manipulation and audio production. This research, led by Felix Langfeldt, Joe Tan, Sayan Jana, and Lea Sirota, explores the intriguing behavior of waves in non-reciprocal systems, where the flow of waves is not symmetric, and how these systems can be harnessed to create novel acoustic experiences.
The study focuses on the non-Hermitian skin effect, a peculiar phenomenon where waves accumulate at the boundaries of a non-reciprocal system. This effect can create a barrier that prevents waves from passing through an interface between reciprocal (where the flow of waves is symmetric) and non-reciprocal systems. However, under specific conditions, waves can tunnel through this barrier, much like particles do in quantum mechanics. This tunneling effect is what the researchers aimed to realize in the acoustic domain.
To achieve this, the team proposed an active acoustic metamaterial design. This metamaterial consists of an acoustic waveguide with embedded microphones and loudspeakers in its walls. The researchers started with a discrete non-Hermitian lattice model of the system and derived a hybrid continuous-discrete acoustic model. This model resulted in distributed feedback control laws that dictate how the loudspeakers and microphones should interact to realize the desired wave behavior.
The proposed control laws were validated through simulations using the finite element method, both in the frequency and time domains. These simulations included lumped electro-acoustic loudspeaker models to ensure the accuracy of the results. Additionally, the researchers conducted an experimental demonstration using a waveguide with embedded active unit cells and a digital implementation of the control laws. Both the simulations and experiments successfully observed the tunneling phenomenon, confirming the validity of the proposed design.
The practical applications of this research are vast and exciting. In the field of audio production, this technology could lead to the development of advanced sound isolation techniques, allowing for precise control of sound waves in recording studios and concert halls. It could also enable the creation of novel acoustic devices, such as tunable filters and directional loudspeakers, which could revolutionize the way we experience and manipulate sound. Furthermore, this research could inspire new approaches in other areas of wave physics, such as electromagnetism and quantum mechanics, where non-reciprocal systems and tunneling phenomena play a crucial role. Read the original research paper here.
