<p>This research provides experimental insights into the interactions between vortices in lined double-slit cavities, under simultaneous tangential flow and acoustic excitation. Notably, at high sound pressure levels, noise reduction is governed by the conversion of acoustic energy into vortical kinetic energy and its subsequent dissipation; this work therefore focuses on how the intensity of the tangential flow modulates the acoustic response and vortex–vortex interactions. To achieve synchronous measurement of acoustic responses, pressure fluctuations, and unsteady flow behavior, an integrated setup incorporating microphone arrays, pressure transducers, and particle image velocimetry (PIV) was implemented. The PIV system was synchronized via a field-programmable gate array (FPGA), ensuring precise phase-locked measurements through its real-time computing capability. Analysis of the transmission loss demonstrates that the double-slit configuration yielded greater acoustic attenuation compared to a single-slit geometry. This performance enhancement was found to be more pronounced under conditions of strong flow-convection effects. Subsequently, a comparative analysis was performed to examine the vortex dynamics under both weak and strong flow-convection effects. Under weak flow-convection effects, the separated vortex was primarily transported downstream, while under strong effects, the vortex system merged with the shear layer. Furthermore, the mechanism of acoustic-to-flow energy conversion was investigated through an analysis of pressure pulsations and identified coherent structures. The results revealed that the tangential flow significantly modulates the vortex–vortex interactions, as evidenced by a clear shift in the dominant mode from the interaction of separated vortices to the interaction within the internal cavity vortex system.</p>