The human ear has been honed by millions of years of evolution to best suit our hearing needs. Its spiral shape can also inspire acoustic technologies like ultrasonic transducers, which create and listen for ultrasonic echoes to measure blood flow, detect defects in metal, or assist underwater exploration.

Conventional ultrasonic transducers have symmetrical apertures limited to 1D measurements. By equipping acoustic lenses with spiral patterns like that of the human ear, Nie et al. achieved 3D localization.

The transducer finds an object’s distance by retracing the signal’s path. An acoustic lens intentionally distorts the received signal, enabling the researchers to detect the object’s distance and relative angle.

“From a mathematical perspective, every point on a spiral shape has a different distance from its origin,” said author Sevan Harput. “We designed our acoustic lens using this shape to break the surface symmetry. The sound waves arriving from different directions experience a small but unique distortion that is used as encoding. We can compensate for this small distortion and decipher directional information.”

Despite some localization errors by the lens, the ability to detect an object’s location in 3D presents a range of applications.

“Currently, GPS systems need to use at least three satellites to locate a device on Earth,” Harput said. “Imagine a 3D GPS that requires only one satellite. Our design can be used in optical imaging too, where it might be possible to capture 3D photographs with existing CCD camera technology.”

As they continue to improve their design, the authors hope the scientific community, industry leaders, and science enthusiasts will help envision possibilities presented by 3D localization.

Source: “A human ear-inspired ultrasonic transducer (HEUT) for 3-D localization of sub-wavelength scatterers,” by Luzhen Nie, Matthieu Toulemonde, Meng-Xing Tang, Steven Freear, and Sevan Harput, Applied Physics Letters (2023). The article can be accessed at https://doi.org/10.1063/5.0152029.

This paper is part of the Fundamentals and Applications of Metamaterials: Breaking the Limits Collection, learn more here.