Assessment of Ponderosa Pine Bark Acoustic Properties

To assess the feasibility of using an external microphone array for detecting bark beetle densities in Ponderosa pine trees, we conducted acoustic characterization tests on bark samples. This is crucial because bark beetle sounds are infrequent and attenuated by the bark, making it essential to understand the acoustic properties of the bark to evaluate the potential of this detection method. Our analysis showed that the transverse stress wave velocity ranged from 229 to 823 (m/s), while the longitudinal stress wave velocity ranged from 797 to 2428 (m/s). Both velocities increased as the moisture content of the bark decreased. The Modulus of Elasticity (MOE) varied transversely from 3.0 × 10⁷ to 3.7 × 10⁸ (Pa) and longitudinally from 2.1 × 10⁸ to 8.0 × 10⁸ (Pa). These findings highlight the significant variability in bark’s acoustic properties, which must be taken into account when considering the use of an external microphone array for detecting bark beetle activity.