What is it about?
An active control technique is developed to cancel out the obstructive effect of obstacles throughout a propagating medium. Several loudspeakers are placed along a duct, naturally altering the normal propagation of sound. By employing an active control scheme on these loudspeakers, allowing adjusting gains and losses that each one presents to the propagating sound, a "obstacle-less" situation can been recovered.
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Why is it important?
This is the first experimental realization of a recently theoretical paper pointing out that both perfect transmission through disorder as well as a complete suppression of any variation in a wave’s intensity can be achieved by adding a continuous gain–loss distribution to the disorder.
Perspectives
This article is the result of a fruitful discussion between scientists from two laboratories at EPFL (LTS2 with Hervé Lissek and LWE with Romain Fleury), in close collaboration with TU-Wien (Stefan Rotter). The results might be used to improve the sound transmission between a sound source and a disordered medium, for example for ultrasound imaging through multilayered bodies. Alternatively, it might be used to achieve acoustic furtivity, making physical bodies invisible to acoustic sensors.
Dr. Hervé Lissek
Ecole Polytechnique Fédérale de Lausanne
Read the Original
This page is a summary of: Constant-pressure sound waves in non-Hermitian disordered media, Nature Physics, July 2018, Springer Science + Business Media,
DOI: 10.1038/s41567-018-0188-7.
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