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Developers from the University of Pennsylvania have created localized sound zones, that look like bubbles, where only a person inside the bubble can hear the sound.
Even in enclosed spaces and small rooms, a person in such a sound zone will hear a sound, while those in the vicinity — not.
To do this, the researchers used two ultrasonic transducers that direct waves outside the range of human hearing to acoustic metasurfaces in the form of 3D lenses. The materials and geometry of these surfaces allow for the direction of sound waves in certain areas.
«We use two ultrasonic transducers paired with an acoustic metasurface that emits self-refracting beams that intersect at a specific point A person standing at this point can hear the sound, and anyone standing nearby — no», — explains Professor of Acoustics Yun Jing.
These waves move along crescent-shaped trajectories, intersecting at a certain point. At this point, due to the nonlinear acoustic interaction sound is generated. These waves cannot be heard by themselves; the sound is heard only at the point where they intersect.
The system was tested using a human dummy with microphones in its ears, which imitated human hearing. A second microphone scanned the environment and provided confirmation that sound was only audible at the point where the ultrasonic waves intersected.
«Actual we created a virtual headset Someone within the acoustic zone can hear something that is intended only for them, which allows you to create sound and silent zones», — said Jia-Xin «Jay» Zhong, the lead author of the study.
The speaker system was tested in various conditions, including rooms with normal reverberation. This suggests that it can be used in such rooms as classrooms, vehicles and even in open spaces.
So far, the developers have achieved that the system can transmit sound at a distance of about a meter with a volume of up to 60 decibels, which is roughly the same as a normal conversation.
According to the researchers, they can increase the distance and power of the system by increasing the intensity of the ultrasonic waves.
Previous attempts to create directional sound systems have often relied on the use of large numbers of complex speakers. The Penn State team’s approach, which uses metasurfaces to direct sound, offers a more flexible and accurate solution. However, the installation is extremely large, and it is not yet clear how it can be made smaller for use in modern electronic gadgets
The results of the study are published in the journal PNAS
Source: ZMEScience