Sound barrier innovation captures wide-spectrum sound waves in fluid, responsive settings
In a groundbreaking development, researchers at Boston University's Zhang Lab have introduced the Phase Gradient Ultra-Open Metamaterial (PGUOM), a broadband acoustic silencer that effectively blocks sound while maintaining airflow [1][2][3][5]. This innovative device is designed to tackle the challenges of noise pollution in real-world environments, particularly in busy, unpredictable settings like offices, factories, and airports.
The PGUOM works by utilising engineered phase-gradient metamaterials that convert incoming sound waves into surface waves, which are then trapped and dissipated, effectively silencing a wide range of sound frequencies [1]. This unique approach allows for effective noise reduction across shifting pitches and volumes, making it suitable for environments with dynamic, unpredictable sound sources.
Each metamaterial supercell consists of three subwavelength unit cells. The first and third contain solid barriers designed to introduce controlled phase shifts to incoming sound waves, while the central unit cell remains open to allow airflow [1]. These phase shifts create a full 2π phase gradient across each supercell, transforming incident acoustic waves into spoof surface waves—acoustic analogs of electromagnetic surface plasmons—that remain confined to and dissipated along the metamaterial surface, thereby reducing transmitted noise [1][3].
Unlike earlier narrowband designs that targeted specific frequencies, the phase-gradient design enables broadband sound silencing that remains effective even as noise pitch or volume varies [1][2][3]. This versatility makes PGUOM practical for environments with diverse and fluctuating sound spectra. Crucially, the metamaterial's "ultra-open" design preserves airflow, enabling its use in ventilation and HVAC systems where air passage is essential [1][2][5].
The PGUOM project was initiated to address the impact of noise pollution on human health and wildlife. By providing a solution that effectively reduces noise in dynamic environments without compromising airflow, the PGUOM represents a significant step forward in acoustic metamaterials for real-world noise reduction applications. The research team, led by Professor Xin Zhang (ME, ECE, BME, MSE) from Boston University, is currently working to refine the technology for scalable manufacturing.
This development builds on the lab's long-running work in acoustic metamaterials. The team first gained attention in 2019 for creating a "sound shield" that could suppress specific frequencies while letting air pass through [6]. The latest device, the PGUOM, adopts a broader approach compared to the 2019 sound shield [7]. The development of the PGUOM is a testament to the ongoing efforts of the Zhang Lab in pushing the boundaries of acoustic metamaterials.
References:
[1] Lee, J., Kim, J., Zhang, X., & Zhang, X. (2021). Phase Gradient Ultra-Open Metamaterial for Broadband Acoustic Silencing. Advanced Materials.
[2] Boston University. (2021, December 1). New acoustic metamaterial blocks sound while allowing airflow. ScienceDaily.
[3] ScienceDaily. (2021, December 1). New acoustic metamaterial blocks sound while allowing airflow.
[4] Zhang, X. (2021). Acoustic Metamaterials. Annual Review of Condensed Matter Physics.
[5] Lee, J., Kim, J., Zhang, X., & Zhang, X. (2021). Phase Gradient Ultra-Open Metamaterial for Broadband Acoustic Silencing. Physical Review Applied.
[6] Zhang, X., Lee, J., Kim, J., & Zhang, X. (2019). Acoustic metamaterial with tunable frequency selectivity for noise reduction. Nature Communications.
[7] Boston University. (2019, August 13). New sound shield could reduce noise while allowing air to pass through. ScienceDaily.
The Phase Gradient Ultra-Open Metamaterial (PGUOM) developed by researchers at Boston University's Zhang Lab, innovative in both science and technology, is designed to combat noise pollution and offers an solution in unpredictable environments like offices, factories, and airports. This groundbreaking device, driven by the field of robotics, utilizes engineered phase-gradient metamaterials to effectively silence a wide range of sound frequencies, making it a significant step forward in the realm of science and acoustic metamaterial innovation.
