An acoustic probe comprising a piezoelectric ceramic transducer element energizable to emit ultrasonic signals in a first direction and in a second direction opposite to the first, and mountable on a sample to be tested so as to transmit thereto signals emitted in the said first direction, is further...http://www.google.es/patents/US5481153?utm_source=gb-gplus-sharePatente US5481153 - Acoustic non-destructive testing
