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vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" 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id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Hydrophone</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 36 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-36" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">36 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%B3%D9%85%D8%A7%D8%B9%D8%A9_%D9%85%D8%A7%D8%A6%D9%8A%D8%A9" title="سماعة مائية – Arabic" lang="ar" hreflang="ar" data-title="سماعة مائية" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Hidrofon" title="Hidrofon – Bosnian" lang="bs" hreflang="bs" data-title="Hidrofon" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Hidr%C3%B2fon" title="Hidròfon – Catalan" lang="ca" hreflang="ca" data-title="Hidròfon" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Hydrofon" title="Hydrofon – Czech" lang="cs" hreflang="cs" data-title="Hydrofon" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Hydrophon" title="Hydrophon – German" lang="de" hreflang="de" data-title="Hydrophon" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/H%C3%BCdrofon" title="Hüdrofon – Estonian" lang="et" hreflang="et" data-title="Hüdrofon" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A5%CE%B4%CF%81%CF%8C%CF%86%CF%89%CE%BD%CE%BF" title="Υδρόφωνο – Greek" lang="el" hreflang="el" data-title="Υδρόφωνο" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Hidr%C3%B3fono" title="Hidrófono – Spanish" lang="es" hreflang="es" data-title="Hidrófono" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Hidrofono" title="Hidrofono – Basque" lang="eu" hreflang="eu" data-title="Hidrofono" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%87%DB%8C%D8%AF%D8%B1%D9%88%D9%81%D9%88%D9%86" title="هیدروفون – Persian" lang="fa" hreflang="fa" data-title="هیدروفون" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Hydrophone" title="Hydrophone – French" lang="fr" hreflang="fr" data-title="Hydrophone" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Hidr%C3%B3fono" title="Hidrófono – Galician" lang="gl" hreflang="gl" data-title="Hidrófono" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%80%D5%AB%D5%A4%D6%80%D5%B8%D6%86%D5%B8%D5%B6" title="Հիդրոֆոն – Armenian" lang="hy" hreflang="hy" data-title="Հիդրոֆոն" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Hidrofon" title="Hidrofon – Croatian" lang="hr" hreflang="hr" data-title="Hidrofon" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Hidrofon" title="Hidrofon – Indonesian" lang="id" hreflang="id" data-title="Hidrofon" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Idrofono" title="Idrofono – Italian" lang="it" hreflang="it" data-title="Idrofono" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%94%D7%99%D7%93%D7%A8%D7%95%D7%A4%D7%95%D7%9F" title="הידרופון – Hebrew" lang="he" hreflang="he" data-title="הידרופון" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%93%D0%B8%D0%B4%D1%80%D0%BE%D1%84%D0%BE%D0%BD" title="Гидрофон – Kyrgyz" lang="ky" hreflang="ky" data-title="Гидрофон" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Hydrophonum" title="Hydrophonum – Latin" lang="la" hreflang="la" data-title="Hydrophonum" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Hydrofoon" title="Hydrofoon – Dutch" lang="nl" hreflang="nl" data-title="Hydrofoon" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ne mw-list-item"><a href="https://ne.wikipedia.org/wiki/%E0%A4%B9%E0%A4%BE%E0%A4%87%E0%A4%A1%E0%A5%8D%E0%A4%B0%E0%A5%8B%E0%A4%AB%E0%A5%8B%E0%A4%A8" title="हाइड्रोफोन – Nepali" lang="ne" hreflang="ne" data-title="हाइड्रोफोन" data-language-autonym="नेपाली" data-language-local-name="Nepali" class="interlanguage-link-target"><span>नेपाली</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%8F%E3%82%A4%E3%83%89%E3%83%AD%E3%83%95%E3%82%A9%E3%83%B3" title="ハイドロフォン – Japanese" lang="ja" hreflang="ja" data-title="ハイドロフォン" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Hydrofon" title="Hydrofon – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Hydrofon" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Hydrofon" title="Hydrofon – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Hydrofon" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Gidrofon" title="Gidrofon – Uzbek" lang="uz" hreflang="uz" data-title="Gidrofon" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Hydrofon" title="Hydrofon – Polish" lang="pl" hreflang="pl" data-title="Hydrofon" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Hidrofone" title="Hidrofone – Portuguese" lang="pt" hreflang="pt" data-title="Hidrofone" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%93%D0%B8%D0%B4%D1%80%D0%BE%D1%84%D0%BE%D0%BD" title="Гидрофон – Russian" lang="ru" hreflang="ru" data-title="Гидрофон" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Hydrophone" title="Hydrophone – Simple English" lang="en-simple" hreflang="en-simple" data-title="Hydrophone" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Hidrofon" title="Hidrofon – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Hidrofon" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Hydrofoni" title="Hydrofoni – Finnish" lang="fi" hreflang="fi" data-title="Hydrofoni" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Hydrofon" title="Hydrofon – Swedish" lang="sv" hreflang="sv" data-title="Hydrofon" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%93%D1%96%D0%B4%D1%80%D0%BE%D1%84%D0%BE%D0%BD" title="Гідрофон – Ukrainian" lang="uk" hreflang="uk" data-title="Гідрофон" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Hydrophone" title="Hydrophone – Vietnamese" lang="vi" hreflang="vi" data-title="Hydrophone" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E6%B0%B4%E4%B8%AD%E8%81%BD%E9%9F%B3%E5%99%A8" title="水中聽音器 – Cantonese" lang="yue" hreflang="yue" data-title="水中聽音器" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E6%B0%B4%E4%B8%8B%E8%81%BD%E9%9F%B3%E5%99%A8" title="水下聽音器 – Chinese" lang="zh" hreflang="zh" data-title="水下聽音器" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q798062#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div 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</nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" 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div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Hydraulophone" title="Hydraulophone">hydraulophone</a>, a musical instrument.</div> <p class="mw-empty-elt"> </p><p>A <b>hydrophone</b> (<a href="/wiki/Ancient_Greek_language" class="mw-redirect" title="Ancient Greek language">Ancient Greek</a>: <span lang="grc">ὕδωρ + φωνή</span>, <small><a href="/wiki/Literal_translation" title="Literal translation">lit.</a> </small>'water + sound') is a <a href="/wiki/Microphone" title="Microphone">microphone</a> designed for underwater use, for recording or listening to underwater sound. Most hydrophones contains a piezoelectric transducer that generates an electric potential when subjected to a pressure change, such as a sound wave. </p><p>A hydrophone can also detect airborne sounds but is insensitive of them because it is designed to match the <a href="/wiki/Acoustic_impedance" title="Acoustic impedance">acoustic impedance</a> of water, a denser fluid than air. Sound travels 4.3 times faster in water than in air, and a sound wave in water exerts a pressure 60 times more than what is exerted by a wave of the same amplitude in air. Similarly, a standard microphone can be buried in the ground, or immersed in water if it is put in a waterproof container but will give poor performance because of the similarly-bad acoustic impedance match. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Hydrophone_being_lowered_into_the_Atlantic.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Hydrophone_being_lowered_into_the_Atlantic.jpg/220px-Hydrophone_being_lowered_into_the_Atlantic.jpg" decoding="async" width="220" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Hydrophone_being_lowered_into_the_Atlantic.jpg/330px-Hydrophone_being_lowered_into_the_Atlantic.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Hydrophone_being_lowered_into_the_Atlantic.jpg/440px-Hydrophone_being_lowered_into_the_Atlantic.jpg 2x" data-file-width="3456" data-file-height="2304" /></a><figcaption>A hydrophone being lowered into the North Atlantic</figcaption></figure> <p>The first hydrophones consisted of a tube with a thin membrane covering the submerged end and the observer's ear of the equipment. <sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The design of effective hydrophones must take into account the acoustic resistance of water, which is 3750 times that of air, and so the pressure exerted by a wave of the same intensity in air is increased by a factor of 3750 in water. The American Submarine Signaling Company developed a hydrophone to detect underwater bells rung from lighthouses and lightships. <sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The case was a thick, hollow brass disc 35 centimetres (14 in) in diameter. On one face was a <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style>one-millimetre-thick (<span class="frac"><span class="num">1</span>⁄<span class="den">32</span></span> in) brass diaphragm, which was coupled by a short brass rod to a <a href="/wiki/Carbon_microphone" title="Carbon microphone">carbon microphone</a>. </p> <div class="mw-heading mw-heading3"><h3 id="World_War_I">World War I</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=2" title="Edit section: World War I"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Early in the war, French President <a href="/wiki/Raymond_Poincar%C3%A9" title="Raymond Poincaré">Raymond Poincaré</a> provided <a href="/wiki/Paul_Langevin" title="Paul Langevin">Paul Langevin</a> with the facilities needed to work on a method to locate submarines by the echos from sound pulses. They developed a <a href="/wiki/Piezoelectric" class="mw-redirect" title="Piezoelectric">piezoelectric</a> hydrophone by increasing the power of the signal with a <a href="/wiki/Vacuum_tube" title="Vacuum tube">vacuum tube</a> amplifier; the high <a href="/wiki/Acoustic_impedance" title="Acoustic impedance">acoustic impedance</a> of piezoelectric materials facilitated their use as underwater transducers. The same piezoelectric plate could be vibrated by an electrical oscillator to produce the sound pulses. <sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>The first submarine to be detected and sunk using a primitive hydrophone was the German submarine <i><a href="/wiki/UC-3" class="mw-redirect" title="UC-3">UC-3</a></i> on 23 April 1916. <i>UC-3</i> was detected by the anti-submarine trawler <i>Cheerio</i> as the <i>Cheerio</i> was directly over the <i>UC-3</i>; the <i>UC-3</i> was then caught in a steel net dragged by the trawler, and sank after a large underwater explosion.<sup id="cite_ref-Thomas_4-0" class="reference"><a href="#cite_note-Thomas-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Brodie_5-0" class="reference"><a href="#cite_note-Brodie-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Hydrophone_drawing.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Hydrophone_drawing.jpg/220px-Hydrophone_drawing.jpg" decoding="async" width="220" height="434" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Hydrophone_drawing.jpg/330px-Hydrophone_drawing.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Hydrophone_drawing.jpg/440px-Hydrophone_drawing.jpg 2x" data-file-width="1634" data-file-height="3226" /></a><figcaption>Hydrophones and directional hydrophones using a baffle.</figcaption></figure> <p>Later in the war, the <a href="/wiki/British_Admiralty" class="mw-redirect" title="British Admiralty">British Admiralty</a> belatedly convened a scientific panel to advise on how to combat U-boats. It included the Australian physicist <a href="/wiki/William_Henry_Bragg" title="William Henry Bragg">William Henry Bragg</a> and the New Zealand physicist Sir <a href="/wiki/Ernest_Rutherford" title="Ernest Rutherford">Ernest Rutherford</a>. They concluded that the best hope was to use hydrophones to listen for submarines. Rutherford's research produced his sole patent for a hydrophone. Bragg took the lead in July 1916 and he moved to the Admiralty hydrophone research establishment at <a href="/wiki/Hawkcraig" class="mw-redirect" title="Hawkcraig">Hawkcraig</a> on the <a href="/wiki/Firth_of_Forth" title="Firth of Forth">Firth of Forth</a>. <sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>The scientists set two goals: to develop a hydrophone that could hear a submarine despite the noise generated by the patrol ship carrying the hydrophone, and to develop a hydrophone that could reveal the bearing of the submarine. A bidirectional hydrophone was invented at <a href="/wiki/East_London_College" class="mw-redirect" title="East London College">East London College</a>. They mounted a microphone on each side of a diaphragm in a cylindrical case; when the sounds heard from both microphones have the same intensity, the microphone is in line with the sound source. <sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>Bragg's laboratory made such a hydrophone directional by mounting a baffle in front of one side of the diaphragm. It took months to discover that effective baffles must contain a layer of air. <sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> In 1918, airships of the Royal Naval Air Service engaged in <a href="/wiki/Anti-submarine_warfare" title="Anti-submarine warfare">anti-submarine warfare</a> experimented by trailing dipped hydrophones.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Bragg tested a hydrophone from a captured German U-boat and found it inferior to British models. By the end of the war, the British had 38 hydrophone officers and 200 qualified listeners, paid an additional 4<i>d</i> per day. <sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>From late in World War I until the introduction of active <a href="/wiki/Sonar" title="Sonar">sonar</a> in the early 1920s, hydrophones were the sole method for submarines to detect targets while submerged; they remain useful today. </p> <div class="mw-heading mw-heading2"><h2 id="Directional_hydrophones">Directional hydrophones</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=3" title="Edit section: Directional hydrophones"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A small single cylindrical ceramic <a href="/wiki/Transducer" title="Transducer">transducer</a> can achieve near perfect omnidirectional reception. Directional hydrophones increase sensitivity from one direction using two basic techniques: </p> <div class="mw-heading mw-heading3"><h3 id="Focused_transducers">Focused transducers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=4" title="Edit section: Focused transducers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>This device uses a single <a href="/wiki/Transducer" title="Transducer">transducer</a> element with a dish or conical-shaped sound reflector to focus the signals, in a similar manner to a reflecting telescope. This type of hydrophone can be produced from a low-cost omnidirectional type, but must be used while stationary, as the reflector impedes its movement through water. A new way to direct is to use a spherical body around the hydrophone. The advantage of directivity spheres is that the hydrophone can be moved within the water, ridding it of the interferences produced by a conical-shaped element. </p> <div class="mw-heading mw-heading3"><h3 id="Arrays">Arrays</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=5" title="Edit section: Arrays"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Multiple hydrophones can be arranged in an <a href="/wiki/Microphone_array" title="Microphone array">array</a> so that it will add the signals from the desired direction while subtracting signals from other directions. The array may be steered using a <a href="/wiki/Beamforming" title="Beamforming">beamformer</a>. Most commonly, hydrophones are arranged in a "line array"<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> but may be in many different arrangements depending on what is being measured. As an example, in the article <sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> measuring propeller noise from fleet ships required complex hydrophone array systems to achieve actionable measurements. </p><p><a href="/wiki/SOSUS" title="SOSUS">SOSUS</a> hydrophones, laid on the seabed and connected by underwater cables, were used, beginning in the 1950s, by the <a href="/wiki/U.S._Navy" class="mw-redirect" title="U.S. Navy">U.S. Navy</a> to track movement of <a href="/wiki/Soviet_Union" title="Soviet Union">Soviet</a> submarines during the <a href="/wiki/Cold_War" title="Cold War">Cold War</a> along a line from <a href="/wiki/Greenland" title="Greenland">Greenland</a>, <a href="/wiki/Iceland" title="Iceland">Iceland</a> and the <a href="/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a> known as the <a href="/wiki/GIUK_gap" title="GIUK gap">GIUK gap</a>.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> These are capable of clearly recording extremely low frequency <a href="/wiki/Infrasound" title="Infrasound">infrasound</a>, including many <a href="/wiki/List_of_unexplained_sounds" title="List of unexplained sounds">unexplained ocean sounds</a>. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=6" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Communication_with_submarines" title="Communication with submarines">Communication with submarines</a></li> <li><a href="/wiki/Geophone" title="Geophone">Geophone</a></li> <li><a href="/wiki/Underwater_acoustics" title="Underwater acoustics">Underwater acoustics</a></li> <li><a href="/wiki/Sonar" title="Sonar">Sonar</a></li> <li><a href="/wiki/Reflection_seismology" title="Reflection seismology">Reflection seismology</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=7" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFWood1930" class="citation book cs1">Wood, A. B. (1930). <i>A textbook of sound</i>. London: G. Bell and Sons. pp. <span class="nowrap">446–</span>461.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+textbook+of+sound&rft.place=London&rft.pages=%3Cspan+class%3D%22nowrap%22%3E446-%3C%2Fspan%3E461&rft.pub=G.+Bell+and+Sons&rft.date=1930&rft.aulast=Wood&rft.aufirst=A.+B.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydrophone" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVan_der_Kloot2014" class="citation book cs1">Van der Kloot, William (2014). <i>Great Scientists wage the Great War</i>. Stroud: Fonthill. p. 104.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Great+Scientists+wage+the+Great+War&rft.place=Stroud&rft.pages=104&rft.pub=Fonthill&rft.date=2014&rft.aulast=Van+der+Kloot&rft.aufirst=William&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydrophone" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">Van der Kloot, 2014, pp. 110–112.</span> </li> <li id="cite_note-Thomas-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Thomas_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFThomas1929" class="citation news cs1">Thomas, Lowell (July 1929). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=wt4DAAAAMBAJ&pg=RA1-PA24">"Fighting the Submarine"</a>. <i>Popular Mechanics</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Popular+Mechanics&rft.atitle=Fighting+the+Submarine&rft.date=1929-07&rft.aulast=Thomas&rft.aufirst=Lowell&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dwt4DAAAAMBAJ%26pg%3DRA1-PA24&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydrophone" class="Z3988"></span></span> </li> <li id="cite_note-Brodie-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-Brodie_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrodieBrodie1973" class="citation book cs1">Brodie, Bernard; Brodie, Fawn M. (1973). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=mAsrwMrfaoQC&pg=PA184"><i>From Crossbow to H-bomb: the evolution of tactics and warfare</i></a> (First Midland ed.). Indiana University Press. p. 184. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0253201616" title="Special:BookSources/0253201616"><bdi>0253201616</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=From+Crossbow+to+H-bomb%3A+the+evolution+of+tactics+and+warfare&rft.pages=184&rft.edition=First+Midland&rft.pub=Indiana+University+Press&rft.date=1973&rft.isbn=0253201616&rft.aulast=Brodie&rft.aufirst=Bernard&rft.au=Brodie%2C+Fawn+M.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DmAsrwMrfaoQC%26pg%3DPA184&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydrophone" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text">Wood 1930, p. 457.</span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">Wood 1930, p. 457.</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">Van der Kloot 2014, p. 110.</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">Report AIR 1/645/17/122/304 – National Archives Kew. Airship Hydrophone experiments.</span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text">Van der Kloot 2014, p. 125.</span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAbraham2019" class="citation book cs1">Abraham, Douglas A. (14 February 2019). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=azuIDwAAQBAJ&q=hydrophones+are+arranged+in+a+%22line+array%22&pg=PA39"><i>Underwater Acoustic Signal Processing: Modeling, Detection, and Estimation</i></a>. Springer. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-319-92983-5" title="Special:BookSources/978-3-319-92983-5"><bdi>978-3-319-92983-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Underwater+Acoustic+Signal+Processing%3A+Modeling%2C+Detection%2C+and+Estimation&rft.pub=Springer&rft.date=2019-02-14&rft.isbn=978-3-319-92983-5&rft.aulast=Abraham&rft.aufirst=Douglas+A.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DazuIDwAAQBAJ%26q%3Dhydrophones%2Bare%2Barranged%2Bin%2Ba%2B%2522line%2Barray%2522%26pg%3DPA39&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydrophone" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.bksv.com/en/knowledge/blog/sound/hydrophone-array">Measuring noise at sea with hydrophone arrays systems</a></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text">Mackay, D.G. "<a rel="nofollow" class="external text" href="http://theses.gla.ac.uk/347/01/2008mackayMPhil.pdf">Scotland the Brave? US Strategic Policy in Scotland 1953–1974</a>". <i>Glasgow University, Masters Thesis (research).</i> 2008. Accessed 12 October 2009.</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=8" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Pike, John (1999). <a href="/wiki/SOSUS" title="SOSUS">SOSUS</a>. Retrieved 28 January 2005.</li> <li>Watlington, Frank (1979). <i>How to build & use low-cost hydrophones.</i> (<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0830610790" title="Special:BookSources/0830610790">0830610790</a>)</li> <li>Unknown. <a rel="nofollow" class="external text" href="http://www.ob-ultrasound.net/hydrophone.html">hydrophone</a>. Retrieved 28 January 2005.</li> <li>Unknown. (2005) <a rel="nofollow" class="external text" href="http://www.glossary.oilfield.slb.com/Display.cfm?Term=hydrophone">Schlumberger Oilfield Glossary: Term 'hydrophone'</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090418005434/http://www.glossary.oilfield.slb.com/Display.cfm?Term=hydrophone">Archived</a> 18 April 2009 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>. Retrieved 28 January 2005.</li> <li>Onda Corporation (2015). '<a rel="nofollow" class="external text" href="http://ondacorp.com/Handbook/">Hydrophone Handbook</a>'.</li> <li>Report AIR 1/645/17/122/304 – National Archives Kew. Airship Hydrophone experiments.</li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydrophone&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output 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li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Hydrophones" class="extiw" title="commons:Category:Hydrophones">Hydrophone</a></span>.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="https://www.bksv.com/en/transducers/acoustic/microphones/hydrophones">Hydrophones</a>—Brüel & Kjær hydrophones and research articles</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20071022034253/http://dosits.org/science/measurng/1.htm">DOSITS</a>—Hydrophone introduction at Discovery of Sound in the Sea</li> <li><a rel="nofollow" class="external text" href="http://orcasound.net?07enohpordyhikiw10">orcasound.net</a>—Live hydrophone streams from killer whale habitat</li> <li><a rel="nofollow" class="external text" href="http://pamguard.org">Passive Acoustic Monitoring</a>—Using hydrophones to monitor underwater sounds</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20090122182929/http://sonar-fs.lboro.ac.uk/uag/products/products_hydrophone.html">Build your own hydrophone</a>—free instructions</li> <li><a rel="nofollow" class="external text" href="http://acoustics.co.uk/">Precision Acoustics</a>—Useful resource on hydrophones</li> <li><a rel="nofollow" class="external text" href="https://www.bl.uk/soundarchive">The British Library Sound Archive</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100722003019/http://www.bl.uk/soundarchive">Archived</a> 22 July 2010 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>—Contains many wildlife and atmospheric recordings made using hydrophones.</li> <li><a rel="nofollow" class="external text" href="http://www.teledyne-reson.com/products/hydrophones/">High-quality hydrophones</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150222214712/http://www.teledyne-reson.com/products/hydrophones/">Archived</a> 22 February 2015 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>—High-quality manufacturer of Hydrophones.</li> <li><a rel="nofollow" class="external text" href="https://leaktronics.com">LeakTronics.com</a>—Makers of Professional Swimming Pool Leak Detection Hydrophones</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist 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