Band gaps in metamaterials and phononic crystals provide a way to engineer vibration mitigation into a material’s geometry. Here, we present a comprehensive experimental characterization of band gaps in lattice-resonator metastructures, which have been previously analyzed with finite element simulations, to better understand this phenomenon in 3D-printed materials. We fabricate the metastructures with a new approach to obtain multimaterial structures using stereolithography. We experimentally characterize the material’s frequency-dependent storage and loss modulus over the band gap frequencies to confirm that the measured band gaps are due to geometry and not due to material properties. Experimental results using both frequency sweep and impulse excitations show that band gaps and attenuation efficiencies strongly depend on the lattice geometry as well as loading direction, and a comparison between axial and bending excitation responses reveals frequency ranges of “fluid-like” and “optical-like” behaviors. Comparison between finite element simulations and experimental results demonstrate the robustness of the metastructure design. While the experiments used here are well established, their combination allows us to gain additional insights into band gaps measurements. Specifically, we show that the coherence function, a common concept in signal processing, is a strong predictor of band gaps in linear materials and that the attenuation efficiency inside the measured band gap can be physically limited by fluid–structure interactions.