3COLLA C.Improving the accuracy of impact-echo in testing post-tensioning ducts[J].Review of Quantitative Nondestructive Evaluation,2003(22):1185-1192.
4MULDOON R,CHALKER A,FOFDE M C,et al.Identifying voids in plastic ducts in post-tensioning prestressed concrete members by resonant frequency of impact-echo,SIBIE and tomography[J].Construction and Building Materials,2007(21)527-537.
5Abraham O,Léonard C,Cote P,et al.Time Frequency Analysis of Impact-Echo Signals:Numerical Modeling and Experimental Validation[J].ACI Materials Journal,2000,97(6):645-657.
6Bracewell R.The Fourier Transform and its Applications[M].3d Ed..Chicago:McGraw-Hill Book Co.,2000.436-444.