Overcoming dead zones in ultrasonic sensors with acoustic metamaterial

Ultrasonic sensors are widely used for non-contact distance measurement, but their performance is often limited by the existence of a "dead zone," where objects too close to the sensor cannot be accurately detected. This study proposes a novel approach using Helmholtz resonator-based acoustic metamaterials to enhance time resolution and mitigate the dead zone effect. Theoretical modeling and experimental validation demonstrate that these metamaterials reduce both phase velocity and group velocity, leading to a significant increase in time resolution. Experiments and FEM simulations confirm that as the frequency approaches the resonant frequency of the metamaterial, the group velocity decreases, enabling more precise distance measurements even within the dead zone. This method provides a practical solution for improving ultrasonic sensor accuracy in applications such as automotive sensing, robotics, and non-destructive testing.