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Photophon

"The idea for an installation piece based on the photoacoustic effect arose at the end of 2011. It was also then that Joost Fonteyne invited me to participate in the second round of the RESONANCE Network project. That was perfect timing. The first presentation took place in September 2013 at Intro in Situ in Maastricht.

Componist

Aernhoudt Jacobs

Jaar

2013

Photophon

Resonance

Exploring the almost impossibilities between art and science.

13 t/m 29 september 2013, Workshop Intro in situ
Resonance 30 mei t/m 19 juni, Botanical Gardens, Riga, Latvia

‘Photophon is based upon the so-called photoacoustic effect that was discovered in the late nineteenth century by the brilliant Scottish scientist, inventor and innovator Alexander Graham Bell, who probably is best known as the inventor of the telephone. As a teenager Alexander Bell witnessed how his mother slowly grew deaf, which aroused his very special interest ni all things related to speech, hearing and sound. In 1880, together with his assistant Charles Tainter, he developed a device that transmitted sounds wirelessly, on a beam of light: the photophone. It reflected sunlight from a flexible flat mirror that actuall served as a microphone. When somebody talked against the mirror’s back, the variations in air pressure caused by the soundwaves of the voice moved the flexible material and were literally reflected in variations of the brightness of the mirrored sunlight. One then ‘only’ needed to translate these back into sound…

Optoacoustic/Photoacoustic effect

It was while working on this receiving end of his photophone that Bell discovered the optoacoustic or photoacoustic effect. He found that solid materials that were exposed to a beam of sunlight that was interrupted by a fast turning wheel with slots – thus giving rise to a very rapid series of light pulses – started to produce sounds. The main (though not sole) reason for this is photothermal. The physical explanation goes roughly like this: the material is heated by the light energy that it absorbs which causes it to contract and expand; these movements of the material then give rise to pressure changes in the surrounding air; but that of course means that there will be sound!

Sonical activation

It was this use of strictly ephemeral phenomena to create sonic events that inspired Aernoudt’s artistic re-interpretation and development of Bell’s discovery. “I was mesmerized by the idea”he said, that sounds around us can be created with light. From Bell’s research notes I learned that any material comes with a sonority that will be revealed by hitting it with a strong enough beam of light. Every material has a resonant frequency, but every material can also be sonically activated. And its sound is directly related to its resonant frequencies. For me this was a revelation, touching the world of sounds in its very essence!”

Aernoudt’s work is a fine example of a combination of artistic and scientific research. He has been developing his ‘Photophon’installation in close collaboration with the Laboratory of Acoustics and Thermal Physics of the Catholic Univesity of Leuven in Belgium. I saw a protoype of the elegant and intriguing horn-like object that is to become the sounding heart of the installation, when in May 2013 I visited an exhibition at the IMAL of Overtoon, the Brussels based platform for research, production and distribution of sound and media art that is directed by Aernoudt and Christoph de Boeck.

Horn

“the horn is the last in the chain of elements that together make up the photophonic object that I imagined,: Aernoudt explained. “It acts as a loudspeaker. Because of its specific dimensions, it will amplify some of the frequencies produced by the photoacoustic cell that I built. That cell is a kind of Helmholtz resonator placed at the narrow end of the horn. Eventually the horns  will be between sixty and seventy centimeters long, very narrow at  the one end (abouth three millimeters) and then widening to some twenty-two centimeters at the other end. The precise dimensions are related to the resonance frequency that I work with”