By Adam Blenford
Passengers travelling on luxury cruise liners usually expect to be looked after by their ship's crew.
The deafening weapon looks innocuous at first glance
Yet pirates who tried to hijack a liner off the coast of Somalia met something a little more sophisticated than a warning shot across the bow.
The crew of the Seabourn Spirit quickly changed course and headed out into open water to evade the attackers in small boats who had raked the vessel with rockets and automatic weapons fire.
They also deployed a military-grade sonic weapon.
The long range acoustic device, or LRAD, is a high-tech loudhailer capable of causing permanent damage to hearing from a distance of more than 300 metres (984ft).
Commissioned and designed after the al-Qaeda attack on the USS Cole in Yemen in 2000, the device's manufacturer, the American Technology Corporation (ATC), calls the LRAD a "non-lethal weapon" with a wide range of uses.
The LRAD typifies a new generation of hi-tech weaponry being deployed in conflict zones.
It was bought by the US Navy in 2003, and is regularly used by US and UK forces aiming to prevent attacks on ports at the mouth of the Tigris in southern Iraq.
US troops have also used the LRAD in action in the Iraqi cities of Falluja and Baghdad, and it was deployed for crowd control in New Orleans in the wake of Hurricane Katrina.
The LRAD uses a high energy acoustic beam - in layman's terms, a very loud noise - to disable and disorientate a opponent or a crowd.
The units, which measure 84cm (33 inches) across and weigh 20kg (45lb), cost roughly $30,000 (£17,200) each.
It is an option becoming increasingly popular on board the world's cruise ships, AJ Ballard of ATC told the BBC News website.
"With all the things going on in the world today, if you have a $1bn ship and you can have the ability to make yourself understood at a distance, you'll take it," said Mr Ballard.
While it remains unclear whether the Seabourn Spirit's deployment of the LRAD had an effect on the pirates, ATC boasts that it can issue a "warning tone that influences behaviour and determines intent at safe stand-off distances".
The shrill sound of an LRAD at its loudest sounds something like a domestic smoke alarm, ATC says, but at 150 decibels, it is the aural equivalent to standing 30m away from a roaring jet engine and can cause major hearing damage if misused.
Tour brochures made no mention of high-grade military defences
The manufacturers say the device can also be used as a loudspeaker, enabling operators to be heard "with authority" above the din of a battle, whether in the desert or on the high seas.
Security is an increasing concern for tour operators entrusted with the safety of thousands of passengers each year, most of whom have dug deep for fees that are often more than $10,000 (£5,500) a trip.
"Most of the security guys [on cruise ships] are retired US and British naval officers. We show them the latest and greatest and they've decided it's something they can use," said Mr Ballard.
He praised the cruise sector for being awake to the dangers posed by pirates and, possibly, terrorists.
The security staff on board the Seabourn Spirit also won Mr Ballard's praise.
"We train all the crew in how to adequately operate the device. This time the head of security was an ex-Gurkha from Nepal, and he made some good quick decisions."
LONG RANGE ACOUSTIC DEVICE - 'LRAD'
On full power, the device can emit a concentrated, 150 decibel [dB] high energy acoustic wave, which retains a level of 100dB over distances of 500 metres. Supersonic airliner Concorde emitted about 110dB, most household smoke detectors about 85dB
The wave is focused within a 15-30 degree 'beam', allowing the LRAD to be aimed at a specific target
Persons standing next to the wave will experience 40dB less noise than those directly in its path. Those behind the LRAD unit are shielded by a 60dB reduction in output