A team at the Swiss Federal Institute of Technology in Zurich (ETH) has worked with experts at the University of Edinburgh to develop technology for acoustic illusions in real time. To mask an object, the control sources emit a signal that completely obliterates the sound waves reflected off the object. By contrast, to simulate an object, they produce an acoustic illusion by adding a second signal to the initial acoustic field.
Now, the group headed by Johan Robertsson, Professor of Applied Geophysics at ETH, reported it has successfully masked and simulated the existence of an object measuring roughly 12 centimeters. The scientists also published their findings in the latest edition of the Science Advances journal.
Innovative about this acoustic illusion is that it is available in real time. To achieve the special acoustic effects, the researchers installed a large test facility with microphones and loudspeakers for the project in the Centre for Immersive Wave Experimentation, located within the Switzerland Innovation Park Zurich on the Dübendorf airfield site. A computer calculated which secondary sounds the control sources must produce to achieve the desired augmentation of the initial field.
As a next step, the researchers want to increase the process to three dimensions and extend its functional range. The new process could also produce acoustic illusions under water. A vast array of potential uses in different fields is envisaged, such as sensor technology, architecture and communications, as well as in the education sector. In the earth sciences, the new process will help bridge a “dead zone” between the frequencies of laboratory and field studies. mm