Effect of specimen size on ultrasonic velocity V_LL of a P wave. Legend: (a) Boring of an increment core from a tree (https://i0.wp.com/haglofsweden.com/wp-content/uploads/2020/05/Core550x840.jpg?w=840&ssl=1 accessed 4 May 2023). (b) An increment core of 5 mm diameter in the L and T axes and of several centimetres in the R axis on which are seen the annual rings and the earlywood and the latewood zones of each annual ring (https://patrimoines.laregion.fr/uploads/pics/IMG_7216_m.jpg accessed 10 August 2023). (c) Effect of sample size and wavelength on velocity V_LL for standard specimens and for 5 mm diameter cores and 10 mm diameter cores, and standard specimens of various lengths and transverse sections of 2 cm × 2 cm and 30 cm length ( – 5 mm core, Δ – 10 mm core and o – standard sample). Ultrasonic frequency 80 kHz ([4], Fig. 9, p. 119).