Acoustic asymmetric transmission based on time-dependent dynamical scattering

Area of Science:

• Acoustics
• Wave Physics
• Mechanical Engineering

Background:

• Unidirectional acoustic transmission is crucial for various applications.
• Existing methods involve acoustic Zeeman effects or nonlinear systems.
• Acoustic frequency conversion in time-varying systems offers a new approach.

Purpose of the Study:

• To demonstrate a novel acoustic frequency conversion process in a time-varying system.
• To develop a tunable acoustic unidirectional device.
• To analyze the underlying scattering mechanism theoretically.

Main Methods:

• Utilizing a rotating blade in air to create a time-varying acoustic system.
• Applying acoustic linear time-varying perturbation theory to describe scattering.
• Integrating frequency conversion with acoustic filtering to achieve unidirectionality.

Main Results:

• Acoustic waves scattered from the rotating blade exhibit frequency shifts proportional to rotation speed.
• A tunable acoustic unidirectional device was successfully developed.
• A 20 dB power transmission contrast ratio between counter-propagating directions was achieved at audible frequencies.

Conclusions:

• Acoustic frequency conversion in time-varying systems provides an effective mechanism for unidirectional wave transmission.
• The developed device offers tunable control over acoustic wave propagation.
• This work presents a new pathway for designing advanced acoustic devices.