Stowaway detector hears rumbling turns
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• by David Craik A detector unit designed to Identify stowaways Iii trailers through low frequency sounds such as the rumblings of people's stomachs Is about to go on trial with Lincolnshire haulier John Mann international.
Invented by Neville Carter of Surrey-based Plastic Sensor Technology, the Stowaway Detector Unit is so sensitive that it can measure 'infrasound'—noise that falls below the level of human hearing.
"The SOU can be placed flat on the bed or body of a vehicle, and picks up the groans and grunts and creaks of the human body which normal hearing cannot pick up," says Carter. "Stomach rumbles are the big giveaway." To avoid the problem of ordinary background sounds affecting the readings, the SDU has been designed to only pick up human sounds coming through the chassis. Placing the SDU above the suspension is also designed to minimise interference from ground vibration.
"A green light on the SDU indicates that it has been set up and is working; an amber light indicates a possible intruder; and a red light indicates that intruders are present," says Carter.
David Kite, general manager of John Mann International, which specialises In delivering hanging garments from North Africa, says: "We are plagued by the problem of stowaways. We have tried several methods to detect them In our trailers but none of them have peeved to be 100% effective."
Kite adds that several of his drivers have left the firm because of problems experienced in North Africa, and has strong views on the stowaway problem (CM 23 April-1 May). "They wait at traffic lights and cut brake airlines so the driver can't move his truck." he reports. "While the driver is repairing it they will jump in the back. We've had trailers made with extra-thick roofs but they've even been through that as well."