Time reversal in acoustics

Time-reversal invariance is a very powerful concept in classical and quantum mechanics. However, simple experimental evidence of this concept is difficult to obtain. In the field of acoustic waves, time-reversal experiments may be achieved much more simply by using time-reversal mirrors made of large ultrasonic piezoelectric transducer arrays. This paper describes the principles of time-reversal acoustics and shows the numerous applications of time-reversal mirrors in medical applications (imaging and therapy) as well as in non-destructive testing of solid media (detection of flaws). Experimental results illustrating these applications will be present.