Due to the layer-by-layer deposition process, 3D printed concrete inevitably develops interlayer interfaces that act as inherent defects with significant uncertainty. To enable a quantitative evaluation of such damage, an active wavefield-based acoustic sensing system is developed in this study. Piezoelectric transducers (PZT) are employed as excitation sources, while a laser Doppler vibrometer is used as a non-contact receiver to acquire surface wavefields at multiple measurement points of the printed structure. Based on the signal intensity characteristics extracted from different spatial locations, wavefield-based signal indicators are proposed. Furthermore, signal attenuation functions along different propagation paths are established to quantitatively assess the interlayer damage and internal defects in 3D printed concrete. The damage evaluation results are validated by comparison with X-ray computed tomography (XCT) observations. The results demonstrate that the proposed wavefield-based nondestructive testing method can effectively identify and quantitatively characterize interfacial damage and defects in 3D printed concrete structures, showing strong potential for structural damage assessment and quality control.