Sound focusing in rooms: the time-reversal approach.
New perspectives in audible range acoustics, such as virtual sound space creation and active noise control, rely on the ability of the rendering system to recreate precisely a desired sound field. This ability to control sound in a given volume of a room is directly linked to the capacity to focus acoustical energy both in space and time. However, sound focusing in rooms remains a complicated problem, essentially because of the multiple reflections on obstacles and walls occurring during propagation. In this paper, the technique of time-reversal focusing, well known in ultrasound, is experimentally applied to audible range acoustics. Compared to classical focusing techniques such as delay law focusing, time reversal appears to considerably improve quality of both temporal and spatial focusing. This so-called super-resolution phenomenon is due to the ability of time reversal to take into account all of the different sound paths between the emitting antenna and the focal point, thus creating an adaptive spatial and temporal matched filter for the considered propagation medium. Experiments emphasize the strong robustness of time-reversal focusing towards small modifications in the medium, such as people in motion or temperature variations. Sound focusing through walls using the time-reversal approach is also experimentally demonstrated.
Yon
Sylvain
S
Laboratoire Ondes et Acoustique, Université Paris VII/ESPCI, CNRS UMR 7587, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
Tanter
Mickael
M
Fink
Mathias
M
D000162:Acoustics; D001307:Auditory Perception; D006801:Humans; D009622:Noise / Q000517:prevention & control*; D012931:Social Environment; D013018:Sound Spectrography