Scientists have developed a technique that allows to conceal the impact that objects have on acoustic fields, making…virtually invisible the effects of sound waves on certain surfaces.
The methodology is based on the use of an external microphone ring (used as audio sensors) and an internal ring of speakers (used as audio sources). Analyzing the sound waves picked up by microphones, a computer orders speakers to instantly adjust the acoustic field so that it acts as if the object is not present (invisible). The system is currently compatible with 2D objects up to 12 cm in size. However, researchers expect to be able to implement the application with 3D objects and with a much larger size.
The objective of the research, that is to hide objects from the acoustic point of view, was also undertaken by the capes of invisibility based on metamaterials, which, however, do not guarantee the same compatibility with a wide range of sound frequencies. This type of technology has the potential to be used in any environment where sound waves are recorded and analysed, covering a whole range of scientific applications, such as the study of underground structures or architectural acoustics. In this regard, researchers hope to obtain in the near future a system that can replicate the characteristics of ‘invisibility’ underwater, where acoustics is significantly different. The sound waves have been the protagonists of our recent article, where they are used to levitate objects through acoustic levitation technology.
The image at the bottom represents the experimental setup of the ring of microphones and speakers. (source: ETH Zurich/Astrid Robertsson)