Creating localized sound zones for audio privacy is particularly challenging at low frequencies, where conventional loudspeakers require large and complex arrays to counteract diffraction. To overcome this limitation, we introduce audible enclaves, which are highly localized audio spots formed through the nonlinear interaction of two self-bending ultrasonic beams. These beams are generated using an acoustic metasurface, enabling them to steer around obstacles and form a localized listening zone in the acoustic shadow. Both simulations and experiments demonstrate an ultrabroadband performance spanning 125 Hz to 4 kHz. The technique is compact (only 0.16 m in size) and remains effective with wideband transient signals, even in moderately reverberant environments. Our proposed audible enclaves hold significant potential for various applications in advanced audio engineering, including private speech communications, immersive spatial audio reproduction, and high-resolution sound/quiet zone control.
Zhong et al. (Wed,) studied this question.