Accurately simulating and designing the vibro-acoustic performance of 3D printed structures is a challenging task due to the lack of material elastic properties, particularly when designing without specialized measurement instruments. To tackle this issue, we propose a numerical-experimental estimation method based on modal impact sound, which only requires a microphone for measurement. Specifically, we established a modal impact sound simulation pipeline that considers the material anisotropy and estimated the material elastic property by minimizing the residuals between the simulated and recorded modal impact sound features. Our method outperforms the state-of-the-art modal-sound approach in terms of convergence speed and accuracy, and achieves an average modal-frequency residual of 0.66% across two materials and six infills. We also designed and manufactured a xylophone using the estimated material elasticity for further demonstration and verification.