HONOLULU, Dec. 3, 2025 — Have you ever tried yelling underwater? Not only is it difficult to make the noise, but it is rarely audible to those outside of the water. Sound travels differently in mediums of different densities, and that causes a high acoustic impedance ratio between air and water, meaning that sound waves have a tough time breaking the air-water barrier, and most of the sound waves reflect off the barrier rather than penetrating it.
To help sound travel between these two mediums, Rutgers University doctoral student Hesam Bakhtiary Yekta simulated a metamaterial that will sit at the air-water interface and improve sound transmission.
Bakhtiary Yekta will present his analysis of the metamaterial Wednesday, Dec. 3, at 9:30 a.m. HST as part of the Sixth Joint Meeting of the Acoustical Society of America and Acoustical Society of Japan, running Dec. 1-5 in Honolulu, Hawaii.
His metamaterial is made from three parallel plates with "ribs" separating them. Sitting at the boundary between air and water, it works by passing the vibrations through its structure, helping to transfer the energy between the air and water.
"One of the reasons our design stands out from others is its simplicity," said Bakhtiary Yekta. "The structure consists of three aluminum plates, which is a common and easily available material. The plates are connected by steel pillar ribs … which hold the structure together and define its acoustic and resonant behavior."
Bakhtiary Yekta hopes that his metamaterial will help facilitate communication between underwater and airborne vehicles, such as an underwater robot and a drone.
"The robot could send an acoustic signal at a specific frequency toward the structure, which is designed to resonate at that frequency and allow the sound to pass from water into air," Bakhtiary Yekta said. "This would make acoustic communication between the two environments possible using a passive mechanism with a decent bandwidth."
Bakhtiary Yekta has already filed a provisional patent for his design.
"My next goal is to continue developing the patent and explore the possibility of running an experiment to verify our simulation and theoretical results," Bakhtiary Yekta said.
