A 3D-printed acoustic metasurface developed by researchers at Penn State could open new possibilities for targeted audio in commercial environments, from museums and retail displays to ticketing terminals and transport hubs.
The research team has designed a speaker covering that can focus audio into a highly localised point in space, creating what it describes as a private “sound spot”. The system manipulates sound waves so they converge at a fixed focal point, allowing audio to be heard clearly in one precise area while becoming dramatically quieter just a short distance away.
The technology is designed for use with parametric array loudspeakers, which use ultrasonic waves to create highly directional sound. These systems are already used in applications such as museums and broadcast spaces where discrete audio delivery is required. However, Penn State researchers say conventional parametric arrays can suffer from limitations, including reflections when sound hits surfaces and weak low-frequency performance.
The new approach uses an acoustic metasurface, a thin structured material that manipulates sound waves in a similar way to how a lens can focus light. The team says the 3D-printed covering can be applied directly to a parametric array loudspeaker to passively focus sound, without the need for complex signal processing or additional power.
In testing, the researchers applied a circular metasurface to an array of parametric loudspeakers, creating a focal point around four inches from the speaker. When a microphone was positioned inside the focal point, it recorded clear, high-quality audio. When it was moved just two inches away, the volume dropped by as much as 50dB.
The research points to potential future applications in spaces where audio needs to be targeted without spilling into the surrounding environment. Use cases could include information points, ATMs, ticketing terminals, retail displays, museum exhibits, control rooms, reception areas and vehicles, where different users may need to hear different audio streams in close proximity.
The system also demonstrated the ability to reproduce frequencies as low as 38Hz, addressing one of the traditional challenges of highly directional audio: limited low-end performance. That could make the technology particularly relevant for applications where sound quality and privacy both matter, rather than simply delivering speech intelligibility at a narrow point.
The acoustic metasurface is around 15cm in diameter and, according to the researchers, could be produced using 3D printing or plastic moulding. While the work remains research-led, it suggests a possible route towards lower-cost, compact directional audio systems that could be integrated into future commercial AV products.
Yun Jing, professor of acoustics at Penn State and corresponding author on the paper, said the metasurface modulates sound waves so that they converge at a central point after leaving the speaker, focusing audio into a precise area.
Jee Woo Kevin Kim, acoustics doctoral candidate and first author of the paper, said the passive nature of the component could reduce the cost of manufacturing and implementing the acoustic metasurface.
Via The Pennsylvania State University
Top image credit: Provided by Jee Woo Kevin Kim. All Rights Reserved.