ScienceNot yet confirmed elsewhere1 publisher2 min readPublished
A sonic black hole printed on its own can be inserted into an existing duct to cut echoes
La Salle researchers designed a 3D-printable sonic black hole that is inserted into an existing duct to reduce echoes, ScienceAlert reported. Conventional versions are built into the pipe, so retrofitting has been difficult.
The Scientist · Science desk
What happened
- The insert is a series of rings mounted on a central rod, with the ring diameters changing gradually along its length.
- In conventional designs, rings and cavities line the inside of the pipe so that sound slows progressively, with shorter wavelengths and more concentrated energy.
- The black-hole effect in those conventional designs works only across a limited range of sound frequencies.
- The team asked whether turning the design inside out would solve both the retrofit problem and the frequency limit.
Why it matters
- capability Ventilation, air-conditioning, exhaust and plumbing runs are the places where echoes build up, and a separately made part could in principle be added to them without replacing pipe.
- constraint In our view the frequency limit of earlier designs is the property to check first, because an insert that works over a narrow band suits a duct dominated by one tone.
- decision Before comparing the insert with a conventional absorber, an operator would want a measured absorption curve across frequency for a real duct.
Under the right conditions, sound waves can be slowed progressively until they effectively never reach the end of their journey. ScienceAlert reports that in a sonic black hole the wave really does slow down as it travels [3]. Oriol Guasch, an acoustics engineer at La Salle, Universitat Ramon Llull, described to the outlet what that would sound like at the closed end of a duct. "If the duct were terminated with a sonic black hole, you would essentially hear no echo at all. Acoustically, it would be almost as if the tube were infinitely long, with no end from which the sound could be reflected back towards you," Guasch told ScienceAlert [1].
He attached a condition to the description. "In the ideal case, once a wave enters the sonic black hole, it does not come back out," Guasch said [2].
The paper is first authored by engineer Jie Deng of La Salle [12]. The inside-out geometry is what lets the part be made on its own, and ScienceAlert calls the result a sonic Christmas tree where the old design was a funnel [14]. "The concept is surprisingly simple, and it works very well," Guasch said. "From a practical point of view, the sonic black hole can be manufactured independently of the duct and then simply inserted into it" [11].
The thing this doesn't tell you is how well it performs. ScienceAlert's account does not report how much echo the insert removes, whether its frequency range is wider than that of the in-pipe designs, or how the rod and rings affect airflow in a ventilation duct. In our view the retrofit claim follows from the geometry, because a rod-and-ring part can be made separately. The performance claim so far rests on Guasch's description.
What to watch
- The published paper's measured echo reduction and frequency range for the inserted version, set against the in-pipe designs.
- Any test of the rod-and-ring part in a duct carrying airflow, since ventilation and exhaust runs are the uses ScienceAlert names.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence45
- Adoption
- Insufficient
- Hype gap+15
- Incentives
- Insufficient
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
"If the duct were terminated with a sonic black hole, you would essentially hear no echo at all. Acoustically, it would be almost as if the tube were infinitely long, with no end from which the sound could be reflected back towards you," Guasch told ScienceAlert.
ReportedSupportedSource: Oriol Guasch, La Salle, Universitat Ramon Llull, to ScienceAlert2 sources— create a free account to open themView cited source - [2]
"In the ideal case, once a wave enters the sonic black hole, it does not come back out," Guasch said.
- [3]
Under the right conditions sound waves can be progressively slowed until they effectively never reach the end of their journey, and in a sonic black hole the wave really does slow down as it travels.
- [4]
Oriol Guasch of La Salle, Universitat Ramon Llull, and colleagues developed a sonic black hole design that can be 3D-printed and inserted directly into an existing pipe.
- [5]
Conventional sonic black hole designs require the black hole to be built into the pipe itself.
- [6]
In conventional designs, a series of rings and cavities lines the inside of the pipe, arranged so that sound waves slow down progressively; their wavelengths become shorter and their energy increasingly concentrated.
- [7]
Conventional sonic black hole structures have to be built into the pipes themselves, usually manufactured together with them, making them difficult to retrofit into existing systems.
- [8]
The black-hole effect in conventional designs only works across a limited range of sound frequencies.
- [9]
Deng, Guasch and their colleagues wondered whether they could solve both the retrofit problem and the limited-frequency problem by turning the whole design inside out.
- [10]
The team's design consists of a series of rings mounted on a central rod, with their diameters gradually changing along its length.
- [11]
"The concept is surprisingly simple, and it works very well," Guasch said. "From a practical point of view, the sonic black hole can be manufactured independently of the duct and then simply inserted into it."
- [12]
The paper describing the design is first authored by engineer Jie Deng of La Salle, Universitat Ramon Llull.
- [13]
Sound travelling through ventilation, air conditioning, industrial exhaust and plumbing pipes can start to rattle around when it meets an obstruction, a change in shape or a closed end.
- [14]
ScienceAlert describes the new design as a sonic Christmas tree where the conventional design was a funnel.
Sources
1 independent publisher whose own reporting we read for this story.
- sciencealert.comPhysicists Built a Black Hole in a Lab. Then It Swallowed Sound.
1 article · October 12, 2026
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- Duct noise controlFollow
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