A Sonic Blaster So Loud, It Could Be Deadly

the thunder generatorDavid Hambling writes for Wired:

All kinds of of devices have been dubbed “sonic blasters” — from the Long Range Acoustic Device super loudhailer to  the piercing Banshee to the Inferno (”most unbearable, gut-wrenching noise I’ve ever heard in my life” according to Danger Room’s own Sharon Weinberger). But a new device, developed in Israel, merits the “sonic blaster” label more than most: the Thunder Generator really is a blaster, producing a series of ear-splitting explosions. Some are so loud, they could be deadly.

Israeli firm PDT Agro developed the Thunder Generator, based on a gadget to scare away birds. The design is very simple: gas from a cylinder of domestic liquid petroleum (LPG) is mixed with air and then detonated, producing a series of high-intensity blasts. Patented “pulse detonation” technology ensures high-decibel blasts. According to Defense News, the Israeli Ministry of Defense has now licensed a firm called ArmyTec to market the Thunder Generator for military and security applications.

The generator can produce up to a hundred blasts a minute, with a 12-kilogram cylinder of gas running to around five thousand blasts. ArmyTec say it can continue for “hours of continous operation,” and suggest that a number of generators could be networked together to cover a wide area. Various configurations are possible, including a curved barrel for firing around corners.

Understandably, the device is designed to be used remotely. It has an effective range of up to fifty meters, and the makers say that it is extremely loud but will not do any lasting damage at this range. However, they warn that within ten meters the Thunder Generator could cause permanent damage or even death (!).

Explosive acoustic weapons are not in themselves a new concept. Explosives are one of the few ways of producing a sound loud enough to have a real effect. The Germans experimented with this in World War II without much success. Back in the 1990’s Primex Physics International carried out development work on a crowd-control  ”acoustic blaster” which combined the output for four separate explosive-driven sources. The device was so large it had to be mounted on a truck, and while the company thought it might one day work out to a hundred meters this was not proven.

The tough part has always been getting the noise to blare in one direction. It is difficult to have an arrangement that can impact the target without deafening the operator. Prolonged exposure is even worse than sort blasts. Electronic devices like LRAD are fairly directional, but are by no means quiet for the user. The Thunder Generator gets around this by allowing the operator be be at a safe distance.

Perhaps it might be more accurate to see the Thunder Generator as a sort of repeating stun grenade; the fuel-air blast it produces is not dissimilar to the fuel-air explosion produced by the new Improved Flash Bang Grenade developed at Sandia National Laboratory. And in at least one case a large number of blast grenades were used for their sonic deterrent effect.

During the Vietnam War, the U.S. operated a number of floating river bases. There was a constant danger of attack from Vietcong swimmers, so they were kept at bay by explosive means, as this memorial site recalls:

“Seafloat was protected from swimmer zapper attacks by throwing concussion grenades into the water from 4 watch stations so that one grenade exploded underneath the ammo pontoons as often as every 30 seconds 24 hours a day. “

This approach seems to have been effective against swimmers, but it also resulted in cracks in the pontoons, which had to be pumped out daily.

The agricultural predecessor of the Thunder Generator has been used in Israel for nearly two years without accident. But there is clearly a risk of leaving an unattended system driven by a gas cannister. And of course there are countermeasures: as a British science program showed last year, with sufficient sound insulation even the LRAD can be damped to a tolderable level.

As with all non-lethals, what happens in practice is likely to be less important than the way it is used. The Thunder Generator could be a good way of keeping stone-throwing youths out of a sensitive area without using excessive force. Or it might be condemned as sonic harassment which exposes whole neighborhoods to incessant noise.

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