<p>The mechanism of hydraulic fractures propagation and interaction is not well understood. Based on on-site experimental data, this paper uses the Discrete Element Method to simulate the hydraulic fracturing process in heterogeneous rock formations, to correlate macroscopic responses (mechanic and acoustic responses) to the contact breakages. The rock model exhibits a brittle failure characterized by injection pressure drops due to cracks. The fracture development is monitored acoustically by measuring both the passive acoustic emission (AE) and the velocity change in the active wave propagation. We have identified cracks as AE sources, and the differences in crack formation result in a dual-frequency characteristic in the AE signals: the low-frequency component is associated with tensile cracks with larger opening, while the high-frequency component corresponds to tension-shear micro-cracks with smaller opening. The location of cracks can be determined by the time-differences analysis. The b-value of AE signals in the Gutenberg-Richter law significantly decreases before the peak injection pressure. Studies of active wave propagation reveal the reduction in P-wave velocity and enhanced coda wave scattering caused by the anisotropic hydraulic fractures. The reduction in P-wave velocity is closely related to the macroscopic stiffness degradation caused by cracks, while correlation analysis effectively distinguishes local fracture intrusion from remote stress disturbances. By combining DEM with acoustic monitoring, this paper intends to provide a comprehensive framework for understanding hydraulic fracture evolution and enhancing fracture detection and characterization.</p>