{"id":663,"date":"2017-09-03T17:36:01","date_gmt":"2017-09-03T15:36:01","guid":{"rendered":"http:\/\/agora.xtec.cat\/col-carmelites\/?page_id=663"},"modified":"2018-10-14T19:56:29","modified_gmt":"2018-10-14T17:56:29","slug":"senyal-daudio","status":"publish","type":"page","link":"https:\/\/agora.xtec.cat\/col-carmelites\/conceptes-tecnics\/senyal-daudio\/","title":{"rendered":"Senyal d&#8217;audio"},"content":{"rendered":"<p>Un\u00a0<b>senyal d&#8217;\u00e0udio<\/b>\u00a0\u00e9s un senyal electr\u00f2nic que \u00e9s una representaci\u00f3 el\u00e8ctrica exacta d&#8217;un senyal sonor. Normalment est\u00e0 fitat al rang de freq\u00fc\u00e8ncies audibles pels \u00e9ssers humans situat entre els 20 i els 20.000\u00a0<a class=\"mw-redirect\" title=\"Hz\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Hz\">Hz<\/a>, aproximadament (gaireb\u00e9 l&#8217;equivalent exacte a 10\u00a0<a title=\"Octava (m\u00fasica)\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Octava_(m%C3%BAsica)\">octaves<\/a>).<\/p>\n<p>At\u00e8s que el so \u00e9s una ona de pressi\u00f3, es requereix un\u00a0<a title=\"Transductor\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Transductor\">transductor<\/a>\u00a0de pressi\u00f3 (un\u00a0<a title=\"Micr\u00f2fon\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Micr%C3%B2fon\">micr\u00f2fon<\/a>) per a convertir les ones de pressi\u00f3 d&#8217;aire (ones sonores) en senyals el\u00e8ctrics (<a title=\"Senyal anal\u00f2gic\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Senyal_anal%C3%B2gic\">senyals anal\u00f2gics<\/a>). La conversi\u00f3 contr\u00e0ria es realitza mitjan\u00e7ant un\u00a0<a title=\"Altaveu\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Altaveu\">altaveu<\/a>, que converteix els senyals el\u00e8ctrics en ones de pressi\u00f3 d&#8217;aire.<\/p>\n<p>Un sol micr\u00f2fon pot captar adequadament tot el rang audible de freq\u00fc\u00e8ncies, en canvi per a reproduir fidedignament aquest mateix rang de freq\u00fc\u00e8ncies solen requerir-se dos altaveus (d&#8217;aguts i greus) o m\u00e9s.<\/p>\n<p>Un senyal d&#8217;\u00e0udio es pot caracteritzar, succintament, per la seva din\u00e0mica (<a class=\"new\" title=\"Valor de pic (encara no existeix)\" href=\"https:\/\/ca.wikipedia.org\/w\/index.php?title=Valor_de_pic&amp;action=edit&amp;redlink=1\">valor de pic<\/a>,\u00a0<a title=\"Rang din\u00e0mic\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Rang_din%C3%A0mic\">rang din\u00e0mic<\/a>,\u00a0<a title=\"Pot\u00e8ncia ac\u00fastica\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Pot%C3%A8ncia_ac%C3%BAstica\">pot\u00e8ncia<\/a>,\u00a0<a title=\"Relaci\u00f3 senyal-soroll\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Relaci%C3%B3_senyal-soroll\">relaci\u00f3 senyal-soroll<\/a>) o pel seu\u00a0<a title=\"Espectre\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Espectre\">espectre<\/a>\u00a0de pot\u00e8ncia (<a title=\"Amplada de banda\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Amplada_de_banda\">amplada de banda<\/a>,\u00a0<a title=\"Freq\u00fc\u00e8ncia\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Freq%C3%BC%C3%A8ncia\">freq\u00fc\u00e8ncia<\/a>\u00a0fonamental,\u00a0<a title=\"Harm\u00f2nic\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Harm%C3%B2nic\">harm\u00f2nics<\/a>,\u00a0<a title=\"Distorsi\u00f3\" href=\"https:\/\/ca.wikipedia.org\/wiki\/Distorsi%C3%B3\">distorsi\u00f3<\/a>harm\u00f2nica, etc.).<\/p>\n<p>Aix\u00ed, per exemple, un senyal que representi veu humana (senyal vocal) no sol tenir informaci\u00f3 rellevant m\u00e9s enll\u00e0 dels 10\u00a0<a class=\"mw-redirect\" title=\"KHz\" href=\"https:\/\/ca.wikipedia.org\/wiki\/KHz\">kHz<\/a>, i de fet en telefonia fixa es prenen nom\u00e9s els primers 4 kHz. Amb 2 kHz n&#8217;hi ha prou perqu\u00e8 la veu sigui comprensible, per\u00f2 no per a recon\u00e8ixer al parlant.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Un\u00a0senyal d&#8217;\u00e0udio\u00a0\u00e9s un senyal electr\u00f2nic que \u00e9s una representaci\u00f3 el\u00e8ctrica exacta d&#8217;un senyal sonor. Normalment est\u00e0 fitat al rang de freq\u00fc\u00e8ncies audibles pels \u00e9ssers humans situat entre els 20 i els 20.000\u00a0Hz, aproximadament (gaireb\u00e9 l&#8217;equivalent exacte a 10\u00a0octaves). At\u00e8s que el so \u00e9s una ona de pressi\u00f3, es requereix un\u00a0transductor\u00a0de pressi\u00f3 (un\u00a0micr\u00f2fon) per a convertir [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":652,"menu_order":10,"comment_status":"closed","ping_status":"closed","template":"page-templates\/side-menu.php","meta":{"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"class_list":["post-663","page","type-page","status-publish","hentry"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/pages\/663","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/comments?post=663"}],"version-history":[{"count":3,"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/pages\/663\/revisions"}],"predecessor-version":[{"id":818,"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/pages\/663\/revisions\/818"}],"up":[{"embeddable":true,"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/pages\/652"}],"wp:attachment":[{"href":"https:\/\/agora.xtec.cat\/col-carmelites\/wp-json\/wp\/v2\/media?parent=663"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}