Xin Zhang, a professor at the College of Engineering, and Reza Ghaffarivardavagh, a Ph.D. student in the Department of Mechanical Engineering at Boston University have released a paper in Physical Review B demonstrating it's possible to silence noise using an open, ringlike structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.
This caught our attention as the choice in studio soundproofing has always been one of attenuation or airflow and as a result one of the most difficult aspects of studio design has always been ventilation. Absorption and labyrinth like structures help but this is usually an area in which compromises have to be made.
"Today's sound barriers are literally thick heavy walls. Although noise-mitigating barricades, called sound baffles, can help drown out the whoosh of rush hour traffic or contain the symphony of music within concert hall walls, they are a clunky approach not well suited to situations where airflow is also critical. Imagine barricading a jet engine's exhaust vent—the plane would never leave the ground. Instead, workers on the tarmac wear earplugs to protect their hearing from the deafening roar.”
Ghaffarivardavagh and Zhang calculated the dimensions and specifications that a metamaterial would need to have in order to interfere with the transmitted sound waves, preventing sound—but not air—from being radiated through the open structure. The basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, they used 3-D printing to create an open, noise-canceling structure made of plastic.
In this video they demonstrate with a loudspeaker on one end of a PVC pipe with a ring of the metamaterial at the other. A sine wave is used in this demonstration, we wonder whether it performs only at a fixed frequency or whether a broadband version is possible?
If you want to know more head over to Phys.org. Would this help studio design? Share your thoughts in the comments below.