Photophon #1, light beams resonating acoustically


What if we could strike an object from a distance and listen to its acoustic qualities using a pulse of light as a projectile? Aernoudt Jacobs has been investigating the field of photoacoustics, inspired by a lesser-known invention patented by Alexander Graham Bell in 1880: the photophone. Conceived as the first wireless telephone, the photophone modulated a condensed beam of sunlight in order to carry the voice of a speaker to a listener situated at a distance. Bell’s invention laid the groundwork for subsequent research into optical transmission of signals that we still employ today in fiber optics and infrared remotes. Captured by the notion that light can be converted directly into sound through the coupling of optical and acoustic elements, Aernoudt Jacobs has been studying this principle in collaboration with the Laboratory of Acoustics and Thermal Physics of the University of Leuven. Photophon #1 is an installation featuring three photoacoustic devices in which a modulated light source is used to excite resonant materials and produce an audible response. A laser beam is interrupted by two rotating perforated discs, generating a stream of luminous pulses that hit a self-made photoacoustic cell. This induces micro-fluctuations in the temperature of the cell, causing the material to expand and contract periodically, generating mechanical oscillations. The amplitude increase necessary to make these vibrations audible is provided by two coupled and precisely tuned acoustic amplifiers, a Helmholtz resonator and an elegantly designed horn of blown glass. Jacobs is now working on a version that will employ a solar tracking system to replace the artificial light source with sunlight. Photophon #1 explores the unrealized aesthetic potential of scientific knowledge by recuperating a 19th century invention through the use of contemporary technologies – and invites us to listen to light beams as music. Matteo Marangoni