We study the phonon behavior of the Co-based honeycomb frustrated magnet Na2Co2TeO6 under a magnetic field applied perpendicular to the honeycomb plane. The temperature and field dependence of the sound velocity and sound attenuation unveil prominent spin-lattice coupling in this material, promoting ultrasound as a sensitive probe for magnetic properties. An out-of-plane ferrimagnetic order is determined below the Néel temperature TN = 27 K. A comprehensive analysis of our data further supports a triple-Q ground state of Na2Co2TeO6. Furthermore, the ultrasound data were systematically compared to the thermal transport results from literature, to unveil the importance of the phononic contribution to the observed transport behaviors.