The function of the metamaterial to modify acoustic waves is created by developing geometries that create phase delays in portions of the wavefront that causes a cancellation of the wave front.\u00a0 Figure 1a<\/em> depicts a sinusoidal wave in red.\u00a0 Figure 1b<\/em> shows the addition of a second wavefront in blue that is precisely out of phase with the first wave.\u00a0 The net result is the straight green line that is the sum of the two waves.\u00a0 More details, including the mathematics involved, are presented in Reference 2<\/strong>.\u00a0<\/p>\n\n\n\n So the question is \u201cWhat can this type of device actually accomplish?\u201d\u00a0 Typically, large and heavy materials are employed to mitigate noises.\u00a0 The typically \u201csound\u201d barriers along the sides of expressways in the cities are a prime example of that approach.\u00a0 But, for individuals who need shielding working in a noisy environment, heavy and bulky is not a solution.\u00a0 Reference 3<\/strong> presents work on a smaller, not large roadside structures, scale that was performed in Professor Xin Zhang\u2019s Boston University\u2019s lab.\u00a0<\/p>\n\n\n\n So, if one has the mathematics background and the computing power to calculate the desired structure shape, how do you prove it works.\u00a0 The researchers decided to create a structure that would cancel the sound from a loudspeaker.\u00a0 Figure 2 <\/em>shown below is a picture of the experimental setup.\u00a0 The video link to its operation is Reference 4<\/strong>.<\/p>\n\n\n\n The bottom portion of the Figure 2<\/em> shows the sound exiting the plastic pipe and the increase in sound, shown by the larger blue area, is obvious when the acoustic silencer is removed.\u00a0 Their calculations indicate that they have reduced the noise level by 94%.<\/p>\n\n\n\n What does that acoustic \u201cplug\u201d look like.\u00a0 The picture below, Figure 3<\/em>, is the plug, which is a 3D printed metamaterial, that modifies acoustic waves in the video in Figure 2<\/em> [Ref. 4<\/strong>].\u00a0<\/p>\n\n\n\n While this structure appears to be simple, the actual internal was not depicted in any of the articles on their work.\u00a0 In order to accomplish the sound cancelling, the structure is complex.\u00a0 There is a video from Duke University [Ref. 5<\/strong>] that provides an explanation of the modification of acoustic waves.\u00a0 Figure 4<\/em> below is a picture from the video in Reference 5<\/strong> with the researchers describing how the different shapes and lengths impact the sound in order to modify it.\u00a0<\/p>\n\n\n\n Obviously, the structure requires some serious design calculations. The ability to change the properties of sound waves with metamaterials that are large in size is due to the fact that sound waves have wavelengths measured in inches.<\/p>\n\n\n\n It is possible that these types of devices could replace the heavy sound blocking partitions along highways with lighter and possibly less costly specifically designed to reduce traffic noises while permitting more traditional neighborhood sounds.<\/p>\n\n\n\n References:<\/strong><\/p>\n\n\n\n Metamaterials are usually identified by indicating it is a constructed material that has characteristics not observed in nature. As the last blog demonstrated, metamaterials at the nanoscale can [..]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-470","post","type-post","status-publish","format-standard","hentry","category-meta"],"_links":{"self":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts\/470","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=470"}],"version-history":[{"count":1,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts\/470\/revisions"}],"predecessor-version":[{"id":478,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts\/470\/revisions\/478"}],"wp:attachment":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=470"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=470"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=470"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"http:\/\/www.nano-blog.com\/wp-content\/uploads\/2022\/07\/Blog-00_2022-07.jpg\")
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