Blind Spotting...

Source: Technology Review

Topics: Acoustics, Humor, Materials Science, Radio Frequency Microelectronics, Sonar

I had the brief temptation to call the post "Bat Sonar," but for the youth that missed the exposure to the campy antics of Adam West/Burt Ward Batman and Robin, the metaphor would have been over their heads due to lack of exposure and severely dated me (not that I haven't numerous times already).

TECHNOLOGY REVIEW: Acoustic "Radar" Spots Stowaways Inside Metal Cargo Containers

Seeing people on the other side of metal walls has never been possible despite the array of high-tech sensors that can peer through other materials. That looks set to change.

The detection of stowaways in lorries, shipping containers, and train carriages is an increasingly important activity as countries all over the world attempt to tackle the illegal movement of people across borders. Various technologies are designed to help but all have significant limitations.

Passive millimeter wave sensors can see through walls but require a source of illumination such as the sky. That generally rules out the detection of stowaways hidden away from sunlight.

Microwave radar systems provide their own source of illumination but generally struggle to detect motionless people. In any case, these signals do not pass through metal walls and so are unsuitable for cargo containers and the such-like.

Then there are systems based on the detection gamma rays. These pass easily through metal walls and are designed primarily for the detection of nuclear materials. But they pose a significant health hazard for humans and so are not suitable for spotting stowaways.

Finally, there are acoustic sensors, which can certainly send signals through metal walls but have never been powerful or sensitive enough to detect humans accurately on the other side.

Until now. Today, all that changes thanks to the work of Franklin Felber at Starmark, a scientific consulting company based in San Diego, who has built and tested an acoustic sensor that is both powerful and sensitive enough to detect the breathing motion of an otherwise stationary human on the other side of a cargo container wall.

Physics arXiv: Demonstration of novel high-power acoustic through-the-wall sensor,
Franklin Felber