{"id":11478,"date":"2018-03-01T02:23:02","date_gmt":"2018-03-01T02:23:02","guid":{"rendered":"http:\/\/www.lifeandnews.com\/articles\/?p=11478"},"modified":"2018-03-02T02:26:01","modified_gmt":"2018-03-02T02:26:01","slug":"can-sound-be-used-as-a-weapon-4-questions-answered","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/can-sound-be-used-as-a-weapon-4-questions-answered\/","title":{"rendered":"Can sound be used as a weapon? 4 questions answered"},"content":{"rendered":"

Kevin Fu<\/a>, University of Michigan<\/a><\/em> and Wenyuan Xu<\/a>, Zhejiang University<\/a><\/em><\/span><\/p>\n

Editor\u2019s note: Government and academic investigators continue to probe<\/a> reports from Cuba that, starting in 2016 and continuing through 2017, U.S. and Canadian diplomats and tourists may have been subjected<\/a> to a \u201csonic weapon<\/a>,\u201d damaging their hearing, causing nausea<\/a>, speech problems<\/a> and potentially even<\/a> mild brain injuries<\/a>.<\/em><\/p>\n

Electrical engineering and computer science professors Wenyuan Xu from Zhejiang University and Kevin Fu from the University of Michigan explain their research, which suggests a more likely scenario of sloppy engineering<\/a>, and what ultrasound frequencies (which can be used to transmit information<\/a> gathered by listening devices<\/a>) traveling through the air can \u2013 and can\u2019t \u2013 do.<\/em><\/p>\n

1. What is ultrasound useful for?<\/h2>\n

The most commonly known use for ultrasound \u2013 high-frequency sound waves human ears can\u2019t hear \u2013 is a medical device<\/a> used for examining a fetus during pregnancy. But there are plenty of other uses.<\/p>\n

Many offices have occupancy sensors that use ultrasound<\/a> to detect movement and keep the lights on when someone is in a space, and off when nobody is around. These sensors operate at frequencies such as 32 kilohertz, far above what the human ear can hear \u2013 which is a range from 20 hertz to 20 kilohertz<\/a>.<\/p>\n

Other products<\/a> use ultrasound to deliver targeted sound<\/a>, for instance allowing a museum to play a recording for visitors in one area of an exhibit without disturbing others nearby. Electronic pest repellents use ultrasound to keep rodents or insects at bay<\/a>.<\/p>\n

A similar product can even be used to disperse teenagers<\/a>; aging tends to reduce people\u2019s ability to hear higher frequency sounds, so a noisemaker can annoy young people without adults even noticing. (This has also let teens create smartphone ringtones<\/a> their elders can\u2019t hear.)<\/p>\n

2. What can go wrong with ultrasound?<\/h2>\n

Airborne ultrasound is not inherently bad. But things can go wrong. A former colleague of Kevin\u2019s used to hear strange sounds from his hearing aid when in rooms with occupancy sensors, likely because the hearing aid\u2019s electronics improperly converted the ultrasound into audible noises. These noises were annoying, but not harmful. A similar problem tainted one of our students\u2019 research, conducted in a room that, unbeknownst to him, had an ultrasonic room occupancy sensor in the ceiling.<\/p>\n

\n \"\"<\/a>
\n Michigan Ph.D. student Connor Bolton frustratingly discovers that ultrasonic noise from a ceiling-mounted room occupancy sensor had interfered with a year\u2019s worth of sonic experiments.<\/span>
\n Connor Bolton<\/span>, CC BY-ND<\/a><\/span>
\n <\/figcaption><\/figure>\n

Both ultrasound and human-audible sound can also affect electronics. For instance, one of us has conducted research in which carefully crafted ultrasonic signals secretly activate voice-control systems<\/a>, even unlocking an iPhone<\/a> with a silent \u201cHey Siri<\/a>\u201d command, and telling it to make a FaceTime call.<\/p>\n

Sound can also affect the physical world, as when a singer shatters a wine glass<\/a>. Microelectrical mechanical sensing chips \u2013 such as accelerometers used in car airbag systems and smartphones, and gyroscopes in drones \u2013 are susceptible to the same interference<\/a>. Those systems can be attacked with sound, crashing a drone mid-flight<\/a>, or fooling a smartphone about whether it\u2019s moving<\/a>.<\/p>\n

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