RT Journal Article SR Electronic A1 Matysik, M. A1 Plskova, I. A1 Korenska, M. A1 Kucharczykova, B. T1 NDT of Mechanical Damaged Concrete Specimens by Nonlinear Acoustic Spectroscopy Method JF Transactions on Transport Sciences YR 2009 VO 2 IS 4 SP 166 OP 171 DO 10.5507/tots.2009.024 UL https://tots.upol.cz/artkey/tot-200904-0004.php AB Current research and development of non-linear ultrasonic spectroscopy methods shows these methods to be very promising for material testing and defectoscopy in the near future. Our experiments focused on the testing of lightweight concrete specimens using the single-frequency excitation method. We studied the concrete specimens' structure after having been stressed by a mechanical force. Measurements were realized before and after mechanical loading.