The passage of ultrasonic waves through an anisotropic inhomogeneous m
aterial such as wood involves complex interactions between the physica
l vibrations of the ultrasound and the elastic response of the wood. T
he initial ultrasound signal is modified by the transmission medium in
a way characteristic of the elastic anisotropy of the medium. The man
y species of wood have subtly different elastic responses. In this wor
k the characteristic signals formed by these responses is examined. A
neural network system is used to classify these signals in terms of sp
ecies. The neural network is shown to have a high success rate in iden
tifying wood species from the ultrasonic trace. It is established that
this identification is not possible using wave velocity or received s
ignal amplitudes. The most appropriate propagation direction for speci
es identification is also considered. (C) 1998 Elsevier Science B.V.