Imagine being able to feel rain on your hands or the texture of a virtual object without touching anything physical. This is possible thanks to acoustic holograms, an emerging technology that uses sound waves to create tactile sensations or manipulate objects in three-dimensional space. Unlike a visual hologram that recreates an image, an acoustic hologram sculpts sound to form high-precision ultrasonic pressure fields.
These 'sound sculptors' work through an array of transducers that emit ultrasonic waves. By precisely controlling the phase and amplitude of each wave, researchers can make them interfere and overlap at specific points in space, creating complex patterns that can be 'felt' or used to exert force. For example, in 2018, scientists at the University of Bristol demonstrated how acoustic holograms can be used to generate force fields capable of levitating small particles or even creating complex tactile illusions in midair.
The applications are vast and fascinating. From contactless haptic interfaces for virtual and augmented reality, which will allow users to 'touch' digital objects, to targeted audio systems that direct sound only to a specific listener in a crowded room. Their potential is also visible in medicine to focus ultrasound noninvasively, or even in manufacturing to assemble microcomponents without physical contact. Acoustic holograms are redefining our interaction with the digital and physical worlds, enabling an immersive experience where sound becomes a tangible tool.
Source: Research from universities such as Bristol and Sussex on ultrasonic haptic interfaces and acoustic levitation. Publications in journals like Nature or Science.
