{"id":273,"date":"2015-07-10T03:55:17","date_gmt":"2015-07-10T03:55:17","guid":{"rendered":"http:\/\/www.kurzweilai.net\/?p=256116"},"modified":"2015-07-13T06:04:45","modified_gmt":"2015-07-13T06:04:45","slug":"a-graphene-microphone-and-loudspeaker-that-operate-at-up-to-500-kilohertz","status":"publish","type":"post","link":"https:\/\/hoo.central12.com\/fugic\/2015\/07\/10\/a-graphene-microphone-and-loudspeaker-that-operate-at-up-to-500-kilohertz\/","title":{"rendered":"A graphene microphone and loudspeaker that operate at up to 500 kilohertz"},"content":{"rendered":"
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Construction of graphene electrostatic wideband receiver (microphone). The graphene membrane is suspended across the supporting frame (A). The membrane is electrically contacted with gold wires, and spacers are added (B) to control the distance from the membrane to the gold-coated stationary electrodes (C). (credit: Qin Zhou et al.\/PNAS)<\/p><\/div>\n

University of California, Berkeley, physicists have used graphene to build lightweight ultrasonic loudspeakers and microphones, enabling people to mimic bats or dolphins\u2019 ability to use sound to communicate and gauge the distance and speed of objects around them.<\/p>\n

More practically, the wireless ultrasound devices complement standard radio transmission using electromagnetic waves in areas where radio is impractical, such as underwater, but with far greater\u00a0fidelity than current ultrasound or sonar devices. They can also be used to communicate through objects, such as steel, that electromagnetic waves can\u2019t penetrate.<\/p>\n

\u201cSea mammals and bats use high-frequency sound for echolocation and communication, but humans just haven\u2019t fully exploited that before, in my opinion, because the technology has not been there,\u201d said UC Berkeley physicist Alex Zettl. \u201cUntil now, we have not had good wideband ultrasound transmitters or receivers. These new devices are a technology opportunity.\u201d<\/p>\n

The diaphragms in the new devices are graphene sheets a mere one atom thick that have the right combination of stiffness, strength and light weight to respond to frequencies ranging from subsonic (below 20 hertz) to ultrasonic (above 20 kilohertz). Humans can hear from 20 hertz up to 20,000 hertz, whereas bats hear only in the kilohertz range, from 9 to 200 kilohertz. The graphene loudspeakers and microphones operate from well below 20 hertz to over 500 kilohertz.<\/p>\n

Practical graphene uses<\/strong><\/p>\n

“There\u2019s a lot of talk about using graphene in electronics and small nanoscale devices, but they\u2019re all a ways away,\u201d said Zettl, who is a senior scientist at Lawrence Berkeley National Laboratory and a member of the Kavli Energy NanoSciences Institute, operated jointly by UC Berkeley and Berkeley Lab. \u201cThe microphone and loudspeaker are some of the closest devices to commercial viability, because we\u2019ve worked out how to make the graphene and mount it, and it\u2019s easy to scale up.\u201d<\/p>\n

Zettl, UC Berkeley postdoctoral fellow Qin Zhou and colleagues describe their graphene microphone and ultrasonic radio in a paper appearing online this week in the\u00a0Proceedings of the National Academy of Sciences<\/em>.<\/p>\n

One big advantage of graphene is that the atom-thick sheet is so lightweight that it responds\u00a0well to the different frequencies of an electronic pulse, unlike today\u2019s piezoelectric microphones and speakers. This comes in handy when using ultrasonic transmitters and receivers to transmit large amounts of information through many different frequency channels simultaneously, or to measure distance, as in sonar applications.<\/p>\n

\u201cBecause our membrane is so light, it has an extremely wide frequency response and is able to generate sharp pulses and measure distance much more accurately than traditional methods,\u201d Zhou said.<\/p>\n

Graphene membranes are also more efficient, converting over 99 percent of the energy driving the device into sound, whereas today\u2019s conventional loudspeakers and headphones convert only 8 percent into sound. Zettl anticipates that in the future, communications devices like cellphones will utilize not only electromagnetic waves \u2013 radio \u2013 but also acoustic or ultrasonic sound, which can be highly directional and long-range.<\/p>\n

Bat chirps<\/h4>\n

Bat expert Michael Yartsev, a newly hired UC Berkeley assistant professor of bioengineering and member of the Helen Wills Neuroscience Institute, said, \u201cThese new microphones will be incredibly valuable for studying auditory signals at high frequencies, such as the ones used by bats.<\/p>\n

The use of graphene allows the authors to obtain very flat frequency responses in a wide range of frequencies, including ultrasound, and will permit a detailed study of the auditory pulses that are used by bats.\u201d<\/p>\n

Zettl noted that audiophiles would also appreciate the graphene loudspeakers and headphones, which have a flat response across the entire audible frequency range.<\/p>\n

The work was supported by the U.S. Department of Energy, the Office of Naval Research and the National Science Foundation. Other co-authors were Zheng, Michael Crommie, a UC Berkeley professor of physics, and Seita Onishi.<\/p>\n

\n

Abstract of\u00a0Graphene electrostatic microphone and ultrasonic radio<\/em><\/h4>\n

We present a graphene-based wideband microphone and a related ultrasonic radio that can be used for wireless communication. It is shown that graphene-based acoustic transmitters and receivers have a wide bandwidth, from the audible region (20\u223c20 kHz) to the ultrasonic region (20 kHz to at least 0.5 MHz). Using the graphene-based components, we demonstrate efficient high-fidelity information transmission using an ultrasonic band centered at 0.3 MHz. The graphene-based microphone is also shown to be capable of directly receiving ultrasound signals generated by bats in the field, and the ultrasonic radio, coupled to electromagnetic (EM) radio, is shown to function as a high-accuracy rangefinder. The ultrasonic radio could serve as a useful addition to wireless communication technology where the propagation of EM waves is difficult.<\/p>\n","protected":false},"excerpt":{"rendered":"

University of California, Berkeley, physicists have used graphene to build lightweight ultrasonic loudspeakers and microphones, enabling people to mimic bats or dolphins’ ability to use sound to communicate and gauge the distance and speed of objects around them. More practically, the wireless ultrasound devices complement standard radio transmission using electromagnetic waves in areas where radio […]<\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[48,43],"tags":[],"class_list":["post-273","post","type-post","status-publish","format-standard","hentry","category-electronics","category-news"],"_links":{"self":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/273"}],"collection":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/comments?post=273"}],"version-history":[{"count":1,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/273\/revisions"}],"predecessor-version":[{"id":274,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/273\/revisions\/274"}],"wp:attachment":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/media?parent=273"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/categories?post=273"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/tags?post=273"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}