A sonic test system has been developed by North American Aviation, Inc., for nondestructively evaluating composite structures throughout their entire depth while requiring access to only one surface. Applications include adhesive‐bonded, diffusion‐bonded, and brazed honeycomb structures. Also, the system has been successfully utilized for testing laminated and corrugated‐core composites. Structural defects such as unbonds, core crushing, and core rupturing are detectable.