Noise pollution increasingly impinges on every facet of modern life, whether indoors or out, urban or rural. Sound baffles can help reduce some of the racket, but most noise-attenuating materials inhibit airflow, limiting the ventilation required for industrial equipment or enclosed areas. Now a new material engineered at Boston The ring-shaped device blocks sound from passing through the middle without blocking air flow. Source: Cydney ScottThe ring-shaped device blocks sound from passing through the middle without blocking air flow. Source: Cydney ScottUniversity promises to diminish the din while admitting air passage.

The acoustic metamaterial is based on Fano-like interference, which refers to interference between two scattering amplitudes, and is configured to block sound without blocking the passage of air through an open structure. The 3D-printed, ring-shaped device counters incoming sound waves and redirects them back the way they came. A helix-like outer coil reduces the sound that can pass through the open center.

To test it, one end of a PVC pipe was sealed with a loudspeaker and the other with the plastic noise-canceling device. Sounds from the speaker were inaudible to the researchers until the metamaterial was removed, and about 94% of the sounds were determined to be attenuated before and after acoustic levels were compared.

The sound silencing material can be synthesized in any shape, and is envisioned for use in mitigating noise from drones, HVAC systems and jet engine exhaust vents. The research appears in Physical Review.