As succinctly phrased by the tagline for “Alien,” the classic sci-fi horror flick, “In space, no one can hear you scream.” The gasses found throughout space are present at densities that are simply far too low to propagate audible sound waves. However, getting out of Earth’s atmosphere and into the silence of the void can be an extremely noisy proposition. Even after the engineers at NASA’s Kennedy Space Center installed a sound suppression system on the launchpads of the space shuttle, the roar of the rockets at ignition reached 142 decibels (dB), roughly twice as powerful as the loudest rock music ever played (139 dB, during a sound check by the heavy metal ensemble Manowar).
Those metalheads would be unusually envious of the engineers of the Large European Acoustic Facility. Located at the European Space Agency’s European Space Research and Technology Centre in Noordwijk, the Netherlands, the LEAF is capable of producing sounds in excess of 154 dB — easily enough to rupture human eardrums. For safety purposes, the facility’s speaker horns can’t even be enabled until all of its doors are securely closed, and a set of half-meter-thick concrete walls and rubber pads keep the volume away from the rest of the research building in which it is housed.
Although these features keep the scientists in charge of LEAF from headbanging to Iron Maiden until the early hours of the morning, they have more important work to conduct: testing spacecraft and satellites against the sound stresses encountered in the violence of a rocket launch. Sound is carried through the air as waves of pressure, and higher dB values represent larger variations of pressure. When buffeted by these waves, the intricate components of the technology being launched into space can be disrupted, affecting the success of important scientific or economic missions. The LEAF technicians expose spacegoing vessels to extreme levels of noise and check for any mechanical or electronic failures, insuring launches against pricey (and embarrassing) mistakes.
The ESA claims that exposure to the LEAF system, when running at full blast, would be enough to kill a listener, but that boast may be slightly exaggerated. While permanent hearing loss might occur, the noise wouldn’t be quite loud enough to damage the internal systems of the body; the threshold for lung rupture and embolism is approximately 200 dB.