<p>➀ A new invention has proven that audio can be transmitted directly to a listener's ears without being audible to others around; </p><p>➁ The technology uses ultrasonic waves beamed through a 3D-printed 'metasurface' to form an audio bubble at the intersection of those waves; </p><p>➂ This could potentially provide listeners personalized audio privacy without the need to wear headphones.</p>