## 1 Introduction  
Wood utility poles are widely applied to facilitate electricity transmission and distribution all over the world due to easy availability, low cost and environmental protection [1; 2]. According to [3], around 5.3 million utility poles made of wood are utilised in Australia, with an appropriate value of more than $12 billion. However, because of exposure to severe environmental conditions, together with fungus and termite attack, wood poles may suffer from the internal deterioration, leading to the strength loss which may cause low reliability of power supply to support daily life. In the last few decades, a large number of non-destructive evaluation (NDE) techniques have been developed to assess the integrity of wood structures, such as wood piles and poles [4; 5; 6; 7; 8; 9; 10]. Sounding is the simplest method for in-situ pole condition assessment, which employs an impact hammer to hit the pole and indicates the void based on a hollow sound. However, this method has the main disadvantage of low accuracy and reliability in results, which are subjective and mainly dependent on the experience of the operator. Furthermore, guided wave is another commonly used NDE method to evaluate the internal damage of wood poles. The guided wave can be produced by a hammer excitation and measured by the accelerometers installed at the side of the structure. Through the study on reflective wave signals, the forecast of health condition of structure will be attempted. However, when the guided wave method is used to evaluate wood poles, the following critical problems should be considered and solved in advance. First of all, wood is a complicated natural material with anisotropic and non-homogeneous features so its material properties are highly influenced by the external environments such as moisture and temperature. As a consequence, the testing accuracy heavily relies on the understanding of wood material features and properties affecting the wave propagation behaviour. Additionally, the surrounding media is changeable during the wave propagation in the wood poles. Generally, an in-situ utility pole is 12 m long with 1.2-1.5 m embedded length underground, which means that the transmission media of wave in the pole changes from air to soil. In this case, the wave behaviour influenced by the transmission media should be considered. The last, but not the least problem, is the excitation position. Ideally, the optimal impact location is the middle top of the pole, where the excitation is able to produce pure longitudinal waves, and longitudinal wave is pretty easy to be analysed, as compared with other possible waves generated in wood poles. Nevertheless, in practical application, the top impact is not available, so the side impact at a reachable height is employed to excite the structure, where longitudinal, bending and surface waves are generated in the meantime, as well as two transmission directions of upward and downward travelling. The prerequisite of condition assessment of wood poles is to understand the complicated wave propagation in pole structure, which is also the objective of this work. In this paper, the numerical studies are conducted to investigate the wave behaviour in in-service wood poles using finite element (FE) analysis. First of all, the FE models of wood pole with isotropic and orthotropic materials are developed considering the soil influence, respectively. Then, to verify the numerical results, experimental testing is carried out based on a 5 m long pole specimen made of wood. An impact hammer and several accelerometers are employed to excite the wave signal and capture the wave propagation response, respectively. The comparison between numerical and experimental results validates that the FE model is able to satisfactorily portray the wave patterns obtained from the experimental testing even though several signal peaks are missed.