Engineers use sound waves to detect bombs remotely

Engineers have developed an acoustic remote bomb detection system that can distinguish between bombs with large or small payloads.

The system uses an acoustic array that focuses an intense sonic beam at a suspected home-made bomb. At the same time, a laser vibrometer—developed for non-destructive inspection of materials—is aimed at the device's casing to measure how the object vibrates in response. The way in which the casing vibrates can offer up information about what is inside.

To put the system to the test, the team created two "bombs"—one was designed to simulate a low-yield explosive while the other was made of a material that simulated a high-yield explosive. Both used hydroxyl-terminated polybutadiene polymer embedded with 50 percent and 75 percent ammonium chloride crystals (by volume) respectively.