The efficacy of acoustic-based Structural Health Monitoring (SHM) systems is intrinsically linked to the signal fidelity and material response of the host composite material. This study investigates the influence of hybrid nanofiller additions, specifically multi-walled carbon nanotubes (MWCNTs), silica (SiO₂), and copper oxide (CuO) nanoparticles on the acoustic signal characteristics of E-glass fiber reinforced polymer composites. The aim is to address the limitations of conventional nano-carbon filled systems which, despite their high damage sensitivity, often suffer from excessive signal attenuation. Seven composite configurations were fabricated with 1 wt% and 3 wt% loadings of individual nanofiller’s (MWCNT, CuO, and SiO₂) and evaluated under ultrasonic excitation. Root Mean Square (RMS) signal voltage was used as a key indicator of acoustic transmission efficiency. The results reveal that MWCNT only composites exhibited significantly damped signals (RMS ~0.5 to 1.5 V), while nano-CuO filled systems maintained high signal clarity (RMS ~7.2 V), even surpassing the unfilled matrix baseline (~6.6 V). Nano-silica composites displayed intermediate behaviour, with modest improvements in RMS values at higher loadings. Most notably, a hybrid system combining MWCNTs with nano-CuO exhibited a synergistic effect, restoring RMS values to approximately 6 V while preserving the damage-responsive damping characteristics associated with MWCNT’s. This balance between signal transmission and flaw sensitivity positions the hybrid composite as a promising material for intelligent SHM applications in aerospace and civil infrastructure. These findings highlight a practical pathway for acoustic optimization through nanofiller engineering, enabling the development of tuneable, structurally responsive materials that enhance the real-time monitoring capabilities of critical systems.