Here\u2019s a shower thought: if light and sound both travel as waves, can you make something that works similarly to a laser but uses sound instead of light?<\/p>\n
It turns out that the answer is \u201cyes\u201d! If you want to see one in action, the YouTube channel Electron Impressions has you covered. The channel\u2019s latest video demonstrates a gun that shoots a narrow beam of soundwaves, along with its most striking property: you can only hear the sound if you\u2019re within the beam\u2019s width. The YouTuber demonstrates this by pointing the device at his camera; when it\u2019s pointing directly at the lens, the music it\u2019s transmitting is clearly audible, but the moment it\u2019s moved away, the music stops.<\/p>\n
So how does the device work? The defining characteristic of laser light is its coherency; lasers produce light of a single wavelength, and the crests of those waves are all aligned. This device works in a similar fashion, but instead of a narrow beam of single-colored light, it creates a narrow beam of sound waves. If these were audible soundwaves, you\u2019d hear them as a single, very loud tone.<\/p>\n
Thankfully, though, the device doesn\u2019t use audible soundwaves. Instead, it operates at a frequency of kHz, which puts it well into the realms of ultrasound, frequencies that are way too high for humans to hear. This allows it to blast out waves at amplitudes that would be extremely loud if they fell into the audible range.<\/p>\n
This is all well and good, but if what we have is a device that\u2019s blasting out a single frequency that\u2019s too high for us to hear anyway, where\u2019s the music coming from?<\/p>\n
The condensed answer is that the ultrasonic frequency acts as what\u2019s called a carrier wave. By superimposing the waveform of the actual music onto the carrier wave, you get a combined signal for transmission; the waveform of the music can be extracted at the other end by subtracting the carrier wave\u2019s waveform from that combined signal. (This is how radio transmissions work.)<\/p>\n
But this raises another question: we can hear radio broadcasts because our radios take the carrier wave and convert it back into audible sound. But there\u2019s no radio in use here, so\u2026 what\u2019s decoding the signal? This is the really clever part, and while a detailed explanation of the answer is beyond the scope of this post, the short version is that the sound basically decodes itself.<\/p>\n
Sound travels at different speeds through low- and high-pressure air, and the ultrasonic beam is powerful enough to cause small changes in the pressure of the air through which it\u2019s traveling. This causes the wave to distort as it travels. This seems like it should be a problem, but instead, the effect is kind of magical: the ultrasonic frequency falls away. Or, as Electron Impressions puts it, \u201cThe air itself demodulates the signal, creating audible sound in mid-air.\u201d<\/p>\n
The result, he continues, \u201cis like having an invisible speaker positioned right in front of your target, making it seem almost as if the sound is being generated inside their head.\u201d It\u2019s a neat party trick, and the video\u2019s comment section is already rife with \u201ccreative\u201d ideas for how such an effect could be used. A note of caution, though: the accompanying write-up contains the caveat that while \u201chigh power ultrasound (over 110dB) has been approved for use in directional sound applications by many health institutions \u2026 there remains some uncertainty as to whether this safety standard should be revisited.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"Here\u2019s a shower thought: if light and sound both travel as waves, can you make something that works…\n","protected":false},"author":2,"featured_media":412768,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[64,63,136,292,128,52397,3973],"class_list":{"0":"post-412767","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-au","9":"tag-australia","10":"tag-music","11":"tag-physics","12":"tag-science","13":"tag-sound","14":"tag-youtube"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/412767","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=412767"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/412767\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/412768"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=412767"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=412767"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=412767"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}