Breaking the symmetry of sound waves allows the sound to be directed to a certain place
Research undertaken by the Universidad Carlos III de Madrid (UC3M) has concluded that sound can be directed to a certain place if the sound waves' symmetry is broken. In order to carry out this work, recently published in the journal Nature, researchers used the whispering gallery phenomenon, a circular, vaulted room in which you can hear what is being said in a specific part of the room from anywhere, even if it is being whispered.
In order to undertake this research, the research team created an artificial whispering gallery in the laboratory that reproduces the same type of effects. Once developed, they added two elements to break the symmetry of the waves, which is what makes it possible to hear the sound from anywhere in the room. On the one hand, they added gain, which allows the waves to be selectively amplified, and, on the other hand, they added topology, which allows the waves to circulate in the desired direction.
"By using specific geometric arrangements, such as topology, we broke this rotational symmetry so that the sound can slide through the whispering gallery in a fully controlled manner. In addition, we also added gain, a property that allows the wave to be amplified in order to break the chiral symmetry (an object's property of not being superposable with image)", notes one of the researchers, Johan Christensen, from the UC3M's Department of Physics.