Insertable Sonic ‘Black Hole’ Reportedly Reduced Sound Reflections in Lab Test

Measuring reflections from rings inserted into a tube

ScienceAlert reports that researchers tested a 3D-printed “sonic black hole”: rings mounted on a central rod that alter how sound travels through a tube. In the laboratory test, microphones measured sound sent by a speaker and the sound reflected back. The report says much of the energy was dissipated through friction and heat exchange at the device’s surfaces.

Conventional sonic-black-hole designs described in the report needed to be built into a pipe, making retrofitting difficult. The report provides no real-duct deployment comparison.

The reported 3D-printed plug-in design was tested in an impedance tube and broadly matched computer simulations for the amount of sound reflected. It did not eliminate echoes, and its performance in real ducts has not been established.

Simulation comparisons differ from real-world deployment

If borne out, the insertable geometry would let an acoustic sound-absorbing structure be made separately and placed in an existing pipe. Simulations cited in the report also suggest less reflected sound than a conventional design over a broader frequency range, but those comparisons are not a real-world deployment.