The author concludes that her mother's occasional efforts at "prettying up to go to the dime store" Oines 78-79) were intellded in part to: uphold an honored practice from the past. attract the attention of men. compete for the full of it with the glamorous wornen in town. apparent purpose. Passage IV versity of Hawaii at Manoa. The routine up-and-down movements of the waves act as a giant loudspeaker, Pushing the air at infrasonic frequencies. Low-frequency sounds are also generated by one 55 of the most colorful displays in the sky, the northern lights. which are caused by charged particles in the air. This electricity heats atmospheric gases, and the warnied gas molecules spread out and increase air pressure. NATURAL SCIENCE: This passage is adapted from the artlcle °Infra8onlc Symphonf by Kale Ramsayer (Q2004 by Science Service). "Let me start off with a riddle." says NASA scien- tist Allan J. Zuckerwar. In his office in Hampton, Va., he rattles off items as dissimilar as rhinoceroses, super- sonic aircraft, and hurricanes. "Now, what do they have 5 in Common?" The answer, Zuckerwar explains, is that each one . generates silent infrasound-long sound waves at a frequency below 20 hertz. People can't hear anything below that frequency, probably for good reason. Otherwise. they'd be bombarded by the con- 10 Stant din of wind, the intermittent groaning of Earth, and the occasional distant explosion. But scientists are eavesdropping on volcanoes, avalanches, earthquakes, and meteorites to discern these phenomena's infrasound signatures and see what new infonnation infrasound 15 might reveal. Just as seismic waves travel through Earth. infra- sonic waves travel t1Ollgh th¢ air. And the lower the frequency of the waves. the fartber they can travel without losing strength. Scientists first detected infra- 20 sound in 1883, when the eruption of the Krakatoa vol- cano in Indonesia sent inaudible sound waves careening around the world, affecting barornetric readings. 60 "It pusbes the neutral air forward, almost like the bow wave off a sl]ip," says Olson. This air movement creates an inftasonic signal. The readings are visible during the beginnings of these magnetic storms. as the bright, greenish ligbts sweep across the sky like a flut- 65 tering curtain. While specialized microphones can pick up infra- sonic signals generated high in the atmosphere, they detect more earthly rumbles, as well. For instance. Jeffrey B. Johnson of the University of Hawaii at 70 Manoa has placed microphones within a kilometer of a vent of the active Erebus volcano in Antarctica. The sensors have recorded low-frequency signals so power- ful tha¢, were they audible, they'd have a volume in excess of 130 decibels-"somewhere between a jet air- 75 plane and tlje threshold of pain,, says Johnson. Erebus does produce some audible sound, but it's not very loud, he says. The infrasound radiating from the volcano's lava lake is generated by tbe rupture of 10-meter-wide, gas- 80 filled bubbles, which pushes huge infrasound waves into the atmosphere. Johnson can use 'infrasound read- ings to estimate the size of the lava bubbles within Erebus and the amount of gas they contain. "Infrasound is a powerful tool to understand more 85 about explosions and eruption sources," says Johnson. "It allows us to directly quantify what's going oll at a volcanic vent." Infrasonic research gained significant attention and funding in the 1950s, when the United States and 25 the Soviet Union used infrasound to detect each other's atmospheric nuclear testing. Interest declined when aboveground bomb testing was bonned in 1963 as part of the Limited Test Ban Treaty. But lately, scientists have turned back to 80 infrasound. IEJfrasound interpretation is a young science. Acousticians and geophysicists are still learning what phenornena generate infrasound signatures and how to match signatures with phenomena. For example, John V. Olson of the University of Alaska in Fairbanks recalls one morning last April when a colleague rushed into his office arid asked whether he had heard an ¢Aplosion the night before. Th¢ two scientists found a large pulse on the infrasound 40 record from the nuclear-test monitorillg station that the University operates and traced it to a nearby firing range. The next day, the local paper Teported that a citi- zen had found a.bundle of dynamite. which police exploded at the range. "So, we take [the signal] out of the 'little green men, file and say, 'This is what dynamite looks like from 5 Miles away." says Olson. "Slowly. daily. we sift and soIt through these signals." Whether infrasound is used for commercial purposes, to learn more about natural phenomena. or 90 .simply to listen for something that nobody wants to bear, it is entering what those in the field call a renaissance. Geopbysicists and acousticians are sorting through, categorizing, and studying a wide range of inaudible noise. 35 Ocean stornis and waves are two of tbe big genera- 50 tors of infrasoulld, says Milton A. Garcés of the Uni-
