Time Reversal simulation

Time Reversal simulation with 2d wave equation with animation.

http://simulations.narod.ru/
It is Time Reversal simulation in Matlab. Black circle is obstacle. Trialgle is detected obstacle position, red points is transmitters/receivers. It is 2d wave equation solution. Borders absorbs waves but not ideally so small reflection from borders exist. The waves are reflected from obstacle. The task is to detect obstacle position. The idea of Time reversal method explained here:
http://en.wikipedia.org/wiki/Time_Reversal_Signal_Processing

Because wave equation has invariant t to -t then transmitters can construct shericle wave that contaract back to the obstacle. First transmitters sends almost plane wave because they inmit gaus pulse simulataneously. Then receivers record response. And then reimit it with t to -t with gain. In this iteration detected position move to real position of the obstacle.