{"id":2366,"date":"2016-08-02T00:04:03","date_gmt":"2016-08-02T00:04:03","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2366"},"modified":"2024-08-23T14:56:33","modified_gmt":"2024-08-23T14:56:33","slug":"qualidades-fisiologicas-do-som","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/ondulatoria\/acustica\/qualidades-fisiologicas-do-som\/","title":{"rendered":"Qualidades fisiol\u00f3gicas do som"},"content":{"rendered":"

Qualidades fisiol\u00f3gicas do som<\/b><\/span><\/span><\/span><\/p>\n

Produ\u00e7\u00e3o e percep\u00e7\u00e3o de ondas sonoras<\/b><\/span><\/span><\/span><\/p>\n

Quando uma <\/b><\/span><\/span>fonte sonora (l\u00e2mina, corda, membrana, etc.) \u00e9 colocada para vibrar, <\/b><\/span><\/span>ela <\/b><\/span><\/span>provoca em toda sua volta, <\/b><\/span><\/span>no <\/b><\/span><\/span>meio que a envolve <\/b><\/span><\/span>(normalmente o ar<\/b><\/span><\/span>), ondas mec\u00e2nicas longitudinais <\/b><\/span><\/span>que, <\/b><\/span><\/span>por meio de sucessivas<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

compress\u00f5es e rarefa\u00e7\u00f5es das part\u00edculas desse meio, viajam em todas as dire\u00e7\u00f5es (meio tridimensional), formando assim, uma onda sonora.<\/b><\/span><\/span><\/p>\n

Essas <\/b><\/span><\/span><\/span>sucessivas compress\u00f5es e rarefa\u00e7\u00f5es simult\u00e2neas <\/b><\/span><\/span><\/span>transferem <\/b><\/span><\/span><\/span>energia <\/b><\/span><\/span><\/span>das <\/b><\/span><\/span><\/span>mol\u00e9culas do ar nas tr\u00eas dimens\u00f5es<\/b><\/span><\/span><\/span>,\u00a0na <\/b><\/span><\/span><\/span>dire\u00e7\u00e3o do movimento da l\u00e2mina corda ou membrana, <\/b><\/span><\/span><\/span>produzindo <\/b><\/span><\/span><\/span>ondas longitudinais, <\/b><\/span><\/span><\/span>nas quais as <\/b><\/span><\/span><\/span>mol\u00e9culas do ar <\/b><\/span><\/span><\/span>se movimentam para frente e para tr\u00e1s,nas <\/b><\/span><\/span><\/span>compress\u00f5es e rarefa\u00e7\u00f5es, <\/b><\/span><\/span><\/span>recebendo <\/b><\/span><\/span><\/span>energia<\/b><\/span><\/span><\/span> das <\/b><\/span><\/span><\/span>mol\u00e9culas mais pr\u00f3ximas da fonte e transmitindo-a para as mol\u00e9culas mais afastadas dela, at\u00e9 chegarem ao ouvido.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

No <\/b><\/span><\/span><\/span>ouvido externo<\/b><\/span><\/span><\/span> onde o <\/b><\/span><\/span><\/span>som \u00e9 captado<\/b><\/span><\/span><\/span>, as <\/b><\/span><\/span><\/span>ondas sonoras atingem uma membrana <\/b><\/span><\/span><\/span>chamada <\/b><\/span><\/span><\/span>t\u00edmpano, <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>passa a vibrar com a mesma freq\u00fc\u00eancia das ondas emitidas pela fonte sonora, <\/b><\/span><\/span><\/span>transmitindo ao <\/b><\/span><\/span><\/span>c\u00e9rebro, <\/b><\/span><\/span><\/span>por meio de termina\u00e7\u00f5es nervosas (nervo ac\u00fastico) os <\/b><\/span><\/span><\/span>impulsos el\u00e9tricos, que os transformam em sensa\u00e7\u00e3o denominada som.<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>som musical, <\/b><\/span><\/span><\/span>que provoca <\/b><\/span><\/span><\/span>sensa\u00e7\u00f5es agrad\u00e1veis, <\/b><\/span><\/span><\/span>\u00e9 produzido por <\/b><\/span><\/span><\/span>vibra\u00e7\u00f5es peri\u00f3dicas.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>ru\u00eddo, <\/b><\/span><\/span><\/span>que provoca <\/b><\/span><\/span><\/span>sensa\u00e7\u00f5es desagrad\u00e1veis, <\/b><\/span><\/span><\/span>\u00e9 produzido por <\/b><\/span><\/span><\/span>vibra\u00e7\u00f5es aperi\u00f3dicas.<\/b><\/span><\/span><\/span><\/p>\n

Qualidades fisiol\u00f3gicas do som<\/b><\/span><\/span><\/span><\/p>\n

S\u00e3o <\/b><\/span><\/span>tr\u00eas as qualidades fisiol\u00f3gicas <\/b><\/span><\/span>do som:\u00a0<\/b><\/span><\/span>intensidade, altura e timbre.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

Intensidade Sonora<\/b><\/span><\/span><\/span><\/p>\n

\u00c8 a <\/b><\/span><\/span>caracter\u00edstica do som <\/b><\/span><\/span>que nos permite <\/b><\/span><\/span>distinguir um som forte de um som fraco <\/b><\/span><\/span>e est\u00e1 <\/b><\/span><\/span>relacionada<\/b><\/span><\/span> com a <\/b><\/span><\/span>energia transportada pela onda <\/b><\/span><\/span>que, <\/b><\/span><\/span>quanto mais perto da fonte mais forte ser\u00e1 o som e mais afastado da fonte, mais fraco.<\/b><\/span><\/span><\/p>\n

Dessa maneira, o <\/b><\/span><\/span>som emitido<\/b><\/span><\/span>, por exemplo, por <\/b><\/span><\/span>uma britadeira<\/b><\/span><\/span>,\u00a0 <\/b><\/span><\/span>ser\u00e1 mais forte para uma pessoa perto da<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

mesma e mais fraco para uma pessoa afastada da mesma.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span>som emitido por um r\u00e1dio funcionando num volume m\u00e1ximo ter\u00e1 maior intensidade <\/b><\/span><\/span>que o <\/b><\/span><\/span>som emitido pelo mesmo r\u00e1dio num volume menor.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span>som<\/b><\/span><\/span> se propaga <\/b><\/span><\/span>num meio material <\/b><\/span><\/span>se <\/b><\/span><\/span>espalhando em todas as dire\u00e7\u00f5es (propaga\u00e7\u00e3o tridimensional) e as frentes de onda t\u00eam formato esf\u00e9rico (superf\u00edcie esf\u00e9rica).<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

Frente de onda<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>\u00e9 a <\/b><\/span><\/span><\/span>regi\u00e3o do espa\u00e7o que re\u00fane todos os pontos do meio alcan\u00e7ados simultaneamente por um pulso <\/b><\/span><\/span><\/span>(dizemos que <\/b><\/span><\/span><\/span>todos os pontos de uma frente de onda t\u00eam a mesma fase, por exemplo, compress\u00f5es ou rarefa\u00e7\u00f5es). <\/b><\/span><\/span><\/span><\/p>\n

As frentes de onda em meios tridimensionais<\/b><\/span><\/span><\/span>, no caso do som, podem ser chamadas de\u00a0<\/b><\/span><\/span><\/span>superf\u00edcies de onda e possuem o formato esf\u00e9rico<\/b><\/i><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

Express\u00e3o matem\u00e1tica da Intensidade Sonora<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>intensidade sonora ou sonoridade <\/b><\/span><\/span><\/span>(I)<\/b><\/span><\/span><\/span> <\/b>de uma onda esf\u00e9rica, num <\/b><\/span><\/span><\/span>determinado ponto, <\/b><\/span><\/span><\/span>\u00e9 <\/b><\/span><\/span><\/span>definida pela express\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"\u00a0<\/span>Se voc\u00ea tiver <\/b><\/span><\/span><\/span>mais que uma frente de onda<\/b><\/span><\/span><\/span>, por exemplo 1 e 2, <\/b><\/span><\/span><\/span>voc\u00ea ter\u00e1:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

As<\/b><\/span><\/span><\/span> intensidades de onda s\u00e3o inversamente proporcionais aos quadrados das dist\u00e2ncias \u00e0 fonte.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

N\u00edvel Sonoro (NS)<\/b><\/span><\/span><\/span><\/p>\n

Mede a <\/b><\/span><\/span><\/span>intensidade sonora <\/b><\/span><\/span><\/span>percebida ou detectada pelo <\/b><\/span><\/span><\/span>sistema auditivo humano. <\/b><\/span><\/span><\/span>\u00c9 medida em <\/b><\/span><\/span><\/span>decibel (dB).<\/b><\/span><\/span><\/span><\/p>\n

Para <\/b><\/span><\/span><\/span>descobrir se o som produzido por uma fonte sonora \u00e9 forte <\/b><\/span><\/span><\/span>(grande intensidade sonora) <\/b><\/span><\/span><\/span>ou fraco (pequena intensidade sonora)<\/b><\/span><\/span><\/span>, determina-se o <\/b><\/span><\/span><\/span>N\u00edvel Sonoro produzido. <\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>n\u00edvel sonoro (NS) relaciona a intensidade sonora de um som com a intensidade sonora do som mais fraco que conseguimos ouvir.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>intensidade m\u00ednima do som percebido pelo ouvido humano <\/b><\/span><\/span><\/span>(<\/b><\/span><\/span><\/span>limiar de audi\u00e7\u00e3o<\/b><\/span><\/span><\/span>) \u00e9, aproximadamente, de <\/b><\/span><\/span><\/span><\/p>\n

10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span><\/span>e se for <\/b><\/span><\/span><\/span>superior a 1W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0ela provocar\u00e1 dor <\/b><\/span><\/span><\/span>(<\/b><\/span><\/span><\/span>limiar da dor<\/b><\/span><\/span><\/span>).<\/b><\/span><\/span><\/span><\/p>\n

Assim, o <\/b><\/span><\/span><\/span>ouvido humano<\/b><\/span><\/span><\/span> pode <\/b><\/span><\/span><\/span>perceber normalmente sons cuja intensidade varie de 10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0a 1Wm<\/b><\/span><\/span><\/span>2.<\/b><\/span><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Como esse <\/b><\/span><\/span><\/span>intervalo aud\u00edvel \u00e9 muito grande, <\/b><\/span><\/span><\/span>utilizamos a <\/b><\/span><\/span><\/span>escala logar\u00edtmica para expressa-lo. <\/b><\/span><\/span><\/span><\/p>\n

Assim, <\/b><\/span><\/span><\/span>definimos\u00a0NS (n\u00edvel sonoro ou n\u00edvel de intensidade ou intensidade auditiva<\/b><\/span><\/span><\/span>)\u00a0de <\/b><\/span><\/span><\/span>determinado som,<\/b><\/span><\/span><\/span> como <\/b><\/span><\/span><\/span>por exemplo<\/b><\/span><\/span><\/span>, o som de <\/b><\/span><\/span><\/span>uma britadeira, de uma sirene, de um conjunto musical, etc., <\/b><\/span><\/span><\/span>como sendo a <\/b><\/span><\/span><\/span>rela\u00e7\u00e3o entre a intensidade desse determinado som (I) e o limiar de audibilidade (I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>).<\/b><\/span><\/span><\/span> <\/b><\/p>\n

O <\/b><\/span><\/span><\/span>n\u00edvel sonoro NS <\/b><\/span><\/span><\/span>\u00e9 medido em <\/b><\/span><\/span><\/span>decibel (dB) e 1dB = 1\/10B<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>n\u00edvel de refer\u00eancia \u00e9 <\/b><\/span><\/span><\/span>I<\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/sub><\/span>= 10<\/b><\/span><\/span><\/span>-12 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>, <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>corresponde <\/b><\/span><\/span><\/span>ao <\/b><\/span><\/span><\/span>som mais fraco que podemos ouvir <\/b><\/span><\/span><\/span>(limiar de audi\u00e7\u00e3o).<\/b><\/span><\/span><\/span><\/p>\n

Express\u00e3o matem\u00e1tica do n\u00edvel sonoro (NS):<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Exemplos de aplica\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

\"\" Para o <\/b><\/span><\/span><\/span>limiar de audibilidade I = 10<\/b><\/span><\/span><\/span>-12 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>n\u00edvel sonoro NS <\/b><\/span><\/span><\/span>ser\u00e1:<\/b><\/span><\/span><\/span><\/p>\n

NS = 10log(I\/I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 NS = 10log(10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 \"\"\u00a0 NS\/10 = log1\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/span>NS\/10 <\/b><\/span><\/span><\/sup><\/span>= 1\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 10<\/b><\/span><\/span><\/span>NS\/10 <\/b><\/span><\/span><\/sup><\/span>= 10<\/b><\/span><\/span><\/span>0\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0\"\"NS\/10 = 0\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>NS = 0.<\/b><\/span><\/span><\/span><\/p>\n

Processo inverso \"\" <\/b><\/span><\/span><\/span> <\/b>quando NS = 0\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span>0 = 10log(I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 0\/10 = log(I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 \"\"\u00a0 0 = log(I\/<\/b><\/span><\/span><\/span><\/p>\n

10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 \"\" 10<\/b><\/span><\/span><\/span>0 <\/b><\/span><\/span><\/sup><\/span>= I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 I=10<\/b><\/span><\/span><\/span>0<\/b><\/span><\/span><\/sup><\/span>.10<\/b><\/span><\/span><\/span>-12\u00a0\u00a0\"\" <\/b><\/span><\/span><\/sup><\/span> <\/b>I = 10<\/b><\/span><\/span><\/span>-12 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

\"\" Para o <\/b><\/span><\/span><\/span>limite da dor I = 1 W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>n\u00edvel sonoro NS <\/b><\/span><\/span><\/span>ser\u00e1:<\/b><\/span><\/span><\/span><\/p>\n

NS = 10log(I\/I<\/b><\/span><\/span><\/span><\/span>o<\/b><\/span><\/span><\/span><\/sub><\/span>)\u00a0 \"\"<\/b><\/span><\/span><\/span><\/span> \u00a0NS = 10log(1\/10<\/b><\/span><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/span><\/sup><\/span>)\u00a0 \"\"\u00a0 NS\/10 = log10<\/b><\/span><\/span><\/span><\/span>12<\/b><\/span><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span><\/span>10<\/b><\/span><\/span><\/span><\/span>NS\/10 <\/b><\/span><\/span><\/span><\/sup><\/span>= 10<\/b><\/span><\/span><\/span><\/span>12<\/b><\/span><\/span><\/span><\/sup><\/span>\u00a0 \"\"<\/b><\/span><\/span><\/span><\/span>\u00a0 NS\/10 = 12\u00a0 \"\"<\/b><\/span><\/span><\/span><\/span>NS = 120 dB.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Processo inverso\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 120 = 10log(I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 \"\"\u00a0 120\/10 = log(I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0\"\"\u00a0 10<\/b><\/span><\/span><\/span>12 <\/b><\/span><\/span><\/sup><\/span>= (I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>) \u00a0\"\"\u00a0 I = 10<\/b><\/span><\/span><\/span>0<\/b><\/span><\/span><\/sup><\/span><\/p>\n

\"\" I = 1 W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

Na <\/b><\/span><\/span><\/span>tabela abaixo fornecemos alguns valores de n\u00edveis sonoros em decib\u00e9is (dB) <\/b><\/span><\/span><\/span>e no <\/b><\/span><\/span><\/span>gr\u00e1fico alguns valores das rela\u00e7\u00f5es entre n\u00edveis sonoros e intensidades <\/b><\/span><\/span><\/span>para voc\u00ea compar\u00e1-los:<\/b><\/span><\/span><\/span><\/p>\n

\u00a0\"\"<\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>n\u00edveis de 90 a 180 decib\u00e9is<\/b><\/span><\/span><\/span> s\u00e3o <\/b><\/span><\/span><\/span>extremamente perigosos no caso de exposi\u00e7\u00e3o constante <\/b><\/span><\/span><\/span>e a <\/b><\/span><\/span><\/span>faixa<\/b><\/span><\/span><\/span> de <\/b><\/span><\/span><\/span>maior sensibilidade do ouvido humano est\u00e1 compreendida entre 1.000Hz e 4.000Hz.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\"<\/p>\n

Altura do som<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>velocidade<\/b><\/span><\/span><\/span> de <\/b><\/span><\/span><\/span>vibra\u00e7\u00e3o da<\/b><\/span><\/span><\/span> fonte sonora (l\u00e2mina, corda, membrana, etc.)<\/b><\/span><\/span> \u00e9 que vai <\/b><\/span><\/span><\/span>definir sua altura.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

As <\/b><\/span><\/span><\/span>vibra\u00e7\u00f5es lentas produzem sons graves <\/b><\/span><\/span><\/span>e as <\/b><\/span><\/span><\/span>vibra\u00e7\u00f5es r\u00e1pidas produzem sons agudos.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

A <\/b><\/span><\/span><\/span>altura dos sons <\/b><\/span><\/span><\/span>depende tamb\u00e9m do <\/b><\/span><\/span><\/span>tamanho dos corpos que vibram<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span>Uma corda fina e curta produz sons mais agudos <\/b><\/span><\/span><\/span>que os de uma <\/b><\/span><\/span><\/span>corda longa e grossa.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Uma <\/b><\/span><\/span><\/span>flauta pequenina de tubo bem fino <\/b><\/span><\/span><\/span>tamb\u00e9m produz <\/b><\/span><\/span><\/span>sons mais agudos <\/b><\/span><\/span><\/span>do que um <\/b><\/span><\/span><\/span>instrumento de sopro com um tubo longo e grosso como a tuba.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>altura do som est\u00e1 relacionada com sua freq\u00fc\u00eancia,<\/b><\/span><\/span><\/span> <\/b>ou seja, a <\/b><\/span><\/span><\/span>altura (tom) \u00e9 a qualidade do som que permite ao ouvido <\/b><\/span><\/span><\/span>distinguir um som grave, de baixa frequ\u00eancia, de um som agudo, de alta freq\u00fc\u00eancia.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span>\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>som mais grave aud\u00edvel <\/b><\/span><\/span><\/span>por um <\/b><\/span><\/span><\/span>ouvido humano <\/b><\/span><\/span><\/span>\u00e9 de aproximadamente <\/b><\/span><\/span><\/span>20 Hz <\/b><\/span><\/span><\/span>e o <\/b><\/span><\/span><\/span>mais agudo <\/b><\/span><\/span><\/span>\u00e9 de<\/b><\/span><\/span><\/span><\/p>\n

aproximadamente <\/b><\/span><\/span><\/span>20 000 Hz.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

Exemplos, calculando a frequ\u00eancia de sons pelo gr\u00e1fico:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Para que <\/b><\/span><\/span><\/span>dois sons distintos possam ser comparados, <\/b><\/span><\/span><\/span>em rela\u00e7\u00e3o \u00e0s suas <\/b><\/span><\/span><\/span>alturas (frequ\u00eancias), define-se entre eles o <\/b><\/span><\/span><\/span>intervalo ac\u00fastico (IA),<\/b><\/span><\/span><\/span> <\/b>atrav\u00e9s da express\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Timbre<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span>timbre <\/b><\/span><\/span>\u00e9 uma <\/b><\/span><\/span>qualidade sonora <\/b><\/span><\/span>que <\/b><\/span><\/span>permite distinguir dois sons de mesma altura <\/b><\/span><\/span>(mesma freq\u00fc\u00eancia) e <\/b><\/span><\/span>mesma intensidade, <\/b><\/span><\/span>emitidos por <\/b><\/span><\/span>instrumentos diferentes tocando a mesma nota musical ou acorde.<\/b><\/span><\/span><\/p>\n

Assim, <\/b><\/span><\/span>conseguimos distinguir se a mesma nota musical \u00e9 emitida por um viol\u00e3o, piano ou saxofone pelo <\/b><\/span><\/span>timbre,<\/b><\/span><\/span> <\/b>pois <\/b><\/span><\/span>ela difere nos tr\u00eas instrumentos<\/b><\/span><\/span> e nos <\/b><\/span><\/span>fornece sensa\u00e7\u00f5es sonoras diferentes, <\/b><\/span><\/span>devido \u00e0s <\/b><\/span><\/span>diferentes composi\u00e7\u00f5es de harm\u00f4nicos gerados por cada instrumento.\u00a0<\/b><\/span><\/span>\"\"<\/p>\n

\u00a0<\/span><\/p>\n

O que voc\u00ea deve saber,informa\u00e7\u00f5es e dicas<\/b><\/span><\/span><\/span><\/p>\n

\"\" A <\/b><\/span><\/span>intensidade do som <\/b><\/span><\/span>est\u00e1 relacionada com a <\/b><\/span><\/span>amplitude.<\/b><\/span><\/span> <\/b>Som mais forte <\/b><\/span><\/span>tem <\/b><\/span><\/span>maior amplitude <\/b><\/span><\/span>e <\/b><\/span><\/span>som mais fraco, menor amplitude.<\/b><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\" Os <\/b><\/span><\/span>n\u00edveis de 90 a 180 decib\u00e9is <\/b><\/span><\/span>s\u00e3o <\/b><\/span><\/span>extremamente perigosos no caso de exposi\u00e7\u00e3o constante.<\/b><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\" A <\/b><\/span><\/span>faixa de maior sensibilidade <\/b><\/span><\/span>do <\/b><\/span><\/span>ouvido humano est\u00e1 compreendida entre 1.000Hz e 4.000Hz.<\/b><\/span><\/span><\/p>\n

\u00a0\"\"<\/span><\/p>\n

\"\" \u00a0<\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\" O <\/b><\/span><\/span>n\u00edvel sonoro total de n fontes id\u00eanticas <\/b><\/span><\/span>\u00e9 dado por <\/b><\/span><\/span>NS(t) = 10.log(n) + L, <\/b><\/span><\/span>onde <\/b><\/span><\/span>L \u00e9 o n\u00edvel sonoro de apenas uma fonte.<\/b><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\" O <\/b><\/span><\/span>timbre \u00e9 uma qualidade sonora <\/b><\/span><\/span>que permite <\/b><\/span><\/span>distinguir dois sons de mesma altura (mesma freq\u00fc\u00eancia<\/b><\/span><\/span>) e <\/b><\/span><\/span>mesma intensidade, <\/b><\/span><\/span>emitidos por instrumentos diferentes <\/b><\/span><\/span>tocando a mesma nota musical ou acorde.<\/b><\/span><\/span><\/p>\n

Assim, <\/b><\/span><\/span>conseguimos distinguir se a mesma nota musical \u00e9 emitida por um viol\u00e3o ou por um piano pelo timbre, <\/b><\/span><\/span>pois <\/b><\/span><\/span>ele difere nos dois instrumentos e <\/b><\/span><\/span>nos fornece sensa\u00e7\u00f5es <\/b><\/span><\/span>sonoras diferentes, <\/b><\/span><\/span>devido \u00e0s diferentes <\/b><\/span><\/span>composi\u00e7\u00f5es de harm\u00f4nicos gerados por cada instrumento.\u00a0<\/b><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\" Altura do som est\u00e1 relacionada com sua freq\u00fc\u00eancia, <\/b><\/span><\/span>ou seja, a <\/b><\/span><\/span>altura (tom) \u00e9 a <\/b><\/span><\/span>qualidade do som <\/b><\/span><\/span>que <\/b><\/span><\/span>permite<\/b><\/span><\/span> ao ouvido distinguir um som grave, de baixa frequ\u00eancia, de um som agudo, de alta freq\u00fc\u00eancia.\u00a0 \u00a0<\/b><\/span><\/span><\/p>\n

\u00a0\"\" Baseado na <\/b><\/span><\/span>equa\u00e7\u00e3o de Taylor <\/b><\/span><\/span>para instrumentos de corda, a <\/b><\/span><\/span>altura (frequ\u00eancia) dos sons emitidos depende<\/b><\/span><\/span> do <\/b><\/span><\/span>comprimento (L) da corda <\/b><\/span><\/span>(rela\u00e7\u00e3o inversa), <\/b><\/span><\/span>da espessura (\u00b5, densidade linear de massa) <\/b><\/span><\/span>da corda <\/b><\/span><\/span>(rela\u00e7\u00e3o inversa) <\/b><\/span><\/span>e da <\/b><\/span><\/span>for\u00e7a de tens\u00e3o (T) <\/b><\/span><\/span>que estica as cordas <\/b><\/span><\/span>(rela\u00e7\u00e3o direta):<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

Assim;<\/b><\/span><\/span><\/p>\n

Quanto <\/b><\/span><\/span>menor<\/b><\/span><\/span> \u00e9 o comprimento das cordas, <\/b><\/span><\/span>mais agudo<\/b><\/span><\/span> (maior frequ\u00eancia) <\/b><\/span><\/span>possui o <\/b><\/span><\/span>som emitido.<\/b><\/span><\/span><\/p>\n

\"\" Quanto <\/b><\/span><\/span>menor<\/b><\/span><\/span> \u00e9 a espessura (<\/b><\/span><\/span>densidade linear de massa <\/b><\/span><\/span>\u00b5) das cordas, <\/b><\/span><\/span>mais agudo<\/b><\/span><\/span> (maior frequ\u00eancia) <\/b><\/span><\/span>possui o <\/b><\/span><\/span>som emitido.<\/b><\/span><\/span><\/p>\n

\"\" Quanto <\/b><\/span><\/span>mais esticadas<\/b><\/span><\/span> <\/b>estiverem as cordas (<\/b><\/span><\/span>maior <\/b><\/span><\/span>for\u00e7a de <\/b><\/span><\/span>tra\u00e7\u00e3o T<\/b><\/span><\/span>)<\/b><\/span><\/span> mais agudo<\/b><\/span><\/span> (maior frequ\u00eancia) <\/b><\/span><\/span>possui o <\/b><\/span><\/span>som emitido.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Numa <\/b><\/span><\/span><\/span>orquestra<\/b><\/span><\/span><\/span>, de forma geral, <\/b><\/span><\/span><\/span>instrumentos da\u00a0fam\u00edlia de cordas <\/b><\/span><\/span><\/span>cujas cordas s\u00e3o <\/b><\/span><\/span><\/span>mais curtas<\/b><\/span><\/span><\/span><\/p>\n

produzem <\/b><\/span><\/span><\/span>sons mais agudos (altos) <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>instrumentos de cordas mais longas, sons mais graves (baixos).<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\"<\/p>\n

Veja a resolu\u00e7\u00e3o de alguns exerc\u00edcios interessantes:<\/b><\/span><\/span><\/span><\/p>\n

01-(FUVEST-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>resultado <\/b><\/span><\/span><\/span>do exame de <\/b><\/span><\/span><\/span>audiometria <\/b><\/span><\/span><\/span>de uma pessoa \u00e9 mostrado nas <\/b><\/span><\/span><\/span>figuras abaixo. <\/b><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>gr\u00e1ficos representam o n\u00edvel de intensidade sonora m\u00ednima I, em decib\u00e9is(dB),<\/b><\/span><\/span><\/span> aud\u00edvel por suas <\/b><\/span><\/span><\/span>orelhas direita e esquerda, <\/b><\/span><\/span><\/span>em <\/b><\/span><\/span><\/span>fun\u00e7\u00e3o<\/b><\/span><\/span><\/span> da <\/b><\/span><\/span><\/span>frequ\u00eancia f <\/b><\/span><\/span><\/span>do som, em <\/b><\/span><\/span><\/span>kHz. <\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>compara\u00e7\u00e3o desse resultado <\/b><\/span><\/span><\/span>com o de <\/b><\/span><\/span><\/span>exames anteriores <\/b><\/span><\/span><\/span>mostrou que, com o <\/b><\/span><\/span><\/span>passar dos anos, ela teve perda auditiva. <\/b><\/span><\/span><\/span>Com <\/b><\/span><\/span><\/span>base <\/b><\/span><\/span><\/span>nessas <\/b><\/span><\/span><\/span>informa\u00e7\u00f5es, <\/b><\/span><\/span><\/span>foram feitas as <\/b><\/span><\/span><\/span>seguintes afirma\u00e7\u00f5es sobre a audi\u00e7\u00e3o dessa pessoa:<\/b><\/span><\/span><\/span><\/p>\n

I.<\/b><\/span><\/span><\/span> <\/b>Ela <\/b><\/span><\/span><\/span>ouve sons de frequ\u00eancia de 6 kHz <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>intensidade de 20 dB<\/b><\/span><\/span><\/span> com a <\/b><\/span><\/span><\/span>orelha direita<\/b><\/span><\/span><\/span>, mas <\/b><\/span><\/span><\/span>n\u00e3o com a esquerda.<\/b><\/span><\/span><\/span><\/p>\n

II.<\/b><\/span><\/span><\/span> <\/b>Um <\/b><\/span><\/span><\/span>sussurro de 15dB e frequ\u00eancia de 0,25 kHz <\/b><\/span><\/span><\/span>\u00e9 ouvido por <\/b><\/span><\/span><\/span>ambas as orelhas.<\/b><\/span><\/span><\/span><\/p>\n

III.<\/b><\/span><\/span><\/span> <\/b>A <\/b><\/span><\/span><\/span>diminui\u00e7\u00e3o de sua sensibilidade auditiva<\/b><\/span><\/span><\/span>, com o <\/b><\/span><\/span><\/span>passar do tempo<\/b><\/span><\/span><\/span>, pode ser atribu\u00edda a <\/b><\/span><\/span><\/span>degenera\u00e7\u00f5es <\/b><\/span><\/span><\/span>dos ossos <\/b><\/span><\/span><\/span>martelo, bigorna e estribo, da orelha externa<\/b><\/span><\/span><\/span>, onde <\/b><\/span><\/span><\/span>ocorre a convers\u00e3o do som em impulsos el\u00e9tricos.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00c9 <\/b><\/span><\/span><\/span>correto apenas <\/b><\/span><\/span><\/span>o que se <\/b><\/span><\/span><\/span>afirma em<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

I.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Falsa<\/b><\/span><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>orelha direita<\/b><\/span><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span> <\/b>observe no gr\u00e1fico que para a orelha <\/b><\/span><\/span><\/span>direita<\/b><\/span><\/span><\/span>, sons de<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>frequ\u00eancia 6 kHz<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>possuem<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>intensidade m\u00ednima de 25 dB, <\/b><\/span><\/span><\/span>ou seja, ele<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>n\u00e3o ouve<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>sons com intensidade<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>abaixo de 25 dB,<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>n\u00e3o ouvindo<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>portanto som de intensidade 20 dB.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Orelha esquerda<\/b><\/span><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span> <\/b>observe no gr\u00e1fico que para a orelha esquerda, sons <\/b><\/span><\/span><\/span>de<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>frequ\u00eancia 6 kHz<\/b><\/span><\/span><\/span><\/p>\n

possuem<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>intensidade m\u00ednima de 10 dB, <\/b><\/span><\/span><\/span>ou seja, ele<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>n\u00e3o ouve<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>sons com intensidade<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>abaixo de 10 dB,<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ouvindo<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>portanto som de intensidade 20 dB.<\/b><\/span><\/span><\/span><\/p>\n

Assim, para a frequ\u00eancia de<\/b><\/span><\/span><\/span> <\/b>6 kHz e n\u00edvel sonoro 20 dB a pessoa<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ouve <\/b><\/span><\/span><\/span>com a <\/b><\/span><\/span><\/span>orelha esquerda, <\/b><\/span><\/span><\/span>mas<\/b><\/span><\/span><\/span><\/p>\n

n\u00e3o<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>com a direita.<\/b><\/span><\/span><\/span><\/p>\n

II. Correta<\/b><\/span><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span> <\/b>para<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ser ouvido<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>um som <\/b><\/span><\/span><\/span>de<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>frequ\u00eancia 0,25 kHz<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>deve possuir<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>intensidade m\u00ednima de <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

10 dB para as duas orelhas,<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ouvindo<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>portanto, um sussurro de<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>15 dB.<\/b><\/span><\/span><\/span><\/p>\n

III. Falsa<\/b><\/span><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span> <\/b>a transforma\u00e7\u00e3o de<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>som em impulso el\u00e9trico<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ocorre na<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>orelha interna<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>onde est\u00e3o localizados os ossos martelo, bigorna e estribo.<\/b><\/span><\/span><\/span><\/p>\n

R- B.<\/b><\/span><\/span><\/span><\/p>\n

02-(UERJ)<\/b><\/span><\/span><\/span> <\/b>Seja <\/b><\/span><\/span><\/span>NS o n\u00edvel sonoro<\/b><\/span><\/span><\/span> de um som, medido em <\/b><\/span><\/span><\/span>decib\u00e9is. <\/b><\/span><\/span><\/span>Esse <\/b><\/span><\/span><\/span>n\u00edvel sonoro <\/b><\/span><\/span><\/span>est\u00e1<\/b><\/span><\/span><\/span><\/p>\n

relacionado com a intensidade do som, I<\/b><\/span><\/span><\/span>, pela f\u00f3rmula abaixo, na qual a <\/b><\/span><\/span><\/span>intensidade padr\u00e3o, I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>, \u00e9 igual a 10<\/b><\/span><\/span><\/span>-12 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

NS = 10.log(I\/I<\/b><\/span><\/span><\/span>0<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span><\/p>\n

Observe a <\/b><\/span><\/span><\/span>tabela ao lado.<\/b><\/span><\/span><\/span> Nela, os <\/b><\/span><\/span><\/span>valores de I foram aferidos a dist\u00e2ncias id\u00eanticas das respectivas fontes de som.<\/b><\/span><\/span><\/span><\/p>\n

Sabendo que <\/b><\/span><\/span><\/span>h\u00e1 riscos de danos ao ouvido m\u00e9dio<\/b><\/span><\/span><\/span> a partir <\/b><\/span><\/span><\/span>de 90dB, quais<\/b><\/span><\/span><\/span> as <\/b><\/span><\/span><\/span>fontes<\/b><\/span><\/span><\/span> da <\/b><\/span><\/span><\/span>tabela<\/b><\/span><\/span><\/span> cuja <\/b><\/span><\/span><\/span>intensidade de emiss\u00e3o de sons est\u00e1 na faixa de risco?<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

Os riscos de danos ao ouvido m\u00e9dio ocorrem<\/b><\/span><\/span><\/span> a partir <\/b><\/span><\/span><\/span>de 90dB \"\" 90 = 10log(I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 9 = logI \u2013 log10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 9 = logI – (-12)log10\u00a0 \"\"\u00a0 9 = logI + 12\u00a0 \"\"\u00a0 -3 = logI\u00a0 \"\" <\/b><\/span><\/span><\/span>I = 10<\/b><\/span><\/span><\/span>-3 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

R-\u00a0Turbina e Amplificador de som<\/b><\/span><\/span><\/span><\/p>\n

03- (UNICAMP-SP)<\/b><\/span><\/span><\/span> <\/b>\u00c9 <\/b><\/span><\/span><\/span>usual <\/b><\/span><\/span><\/span>medirmos o <\/b><\/span><\/span><\/span>n\u00edvel de uma fonte sonora em decib\u00e9is d(B). <\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>n\u00edvel em dB<\/b><\/span><\/span><\/span><\/p>\n

\u00e9 <\/b><\/span><\/span><\/span>relacionado \u00e0 intensidade I da fonte pela f\u00f3rmula N\u00edvel sonoro <\/b><\/span><\/span><\/span>(dB) = 10.log(I\/I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>).<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Em que <\/b><\/span><\/span><\/span>I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0= 10<\/b><\/span><\/span><\/span>-12 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span><\/span>\u00e9 um <\/b><\/span><\/span><\/span>valor padr\u00e3o<\/b><\/span><\/span><\/span> de <\/b><\/span><\/span><\/span>intensidade<\/b><\/span><\/span><\/span> muito <\/b><\/span><\/span><\/span>pr\u00f3ximo do limite de audibilidade humana. <\/b><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>n\u00edveis sonoros necess\u00e1rios <\/b><\/span><\/span><\/span>para uma <\/b><\/span><\/span><\/span>pessoa ouvir variam de indiv\u00edduo para indiv\u00edduo. <\/b><\/span><\/span><\/span><\/p>\n

No <\/b><\/span><\/span><\/span>gr\u00e1fico <\/b><\/span><\/span><\/span>ao <\/b><\/span><\/span><\/span>lado <\/b><\/span><\/span><\/span>esses <\/b><\/span><\/span><\/span>n\u00edveis est\u00e3o representados em fun\u00e7\u00e3o da freq\u00fc\u00eancia do som para dois indiv\u00edduos, A e B. <\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>n\u00edvel sonoro acima do qual <\/b><\/span><\/span><\/span>um ser humano come\u00e7a a<\/b><\/span><\/span><\/span> sentir dor \u00e9 aproximadamente 120dB, independentemente da freq\u00fc\u00eancia.<\/b><\/span><\/span><\/span><\/p>\n

a)<\/b><\/span><\/span><\/span> <\/b>Que <\/b><\/span><\/span><\/span>freq\u00fc\u00eancias o indiv\u00edduo A consegue ouvir melhor que o indiv\u00edduo B?<\/b><\/span><\/span><\/span><\/p>\n

b)<\/b><\/span><\/span><\/span> <\/b>Qual a <\/b><\/span><\/span><\/span>intensidade I m\u00ednima\u00a0 <\/b><\/span><\/span><\/span>de um <\/b><\/span><\/span><\/span>som <\/b><\/span><\/span><\/span>(em W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>)\u00a0 que causa <\/b><\/span><\/span><\/span>dor em um ser humano?<\/b><\/span><\/span><\/span><\/p>\n

c)<\/b><\/span><\/span><\/span> <\/b>Um <\/b><\/span><\/span><\/span>beija flor <\/b><\/span><\/span><\/span>bate suas asas <\/b><\/span><\/span><\/span>100 vezes por segundo<\/b><\/span><\/span><\/span>, emitindo um ru\u00eddo que atinge o <\/b><\/span><\/span><\/span>ouvinte com um n\u00edvel sonoro de 10 dB.<\/b><\/span><\/span><\/span><\/p>\n

Em <\/b><\/span><\/span><\/span>quanto tempo a intensidade I <\/b><\/span><\/span><\/span>desse ru\u00eddo precisa ser <\/b><\/span><\/span><\/span>amplificada para ser aud\u00edvel pelo indiv\u00edduo B?<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>O <\/b><\/span><\/span><\/span>n\u00edvel sonoro (NS) relaciona a intensidade sonora de um som com a intensidade sonora do som mais fraco que conseguimos ouvir.<\/b><\/span><\/span><\/span><\/p>\n

Pelo <\/b><\/span><\/span><\/span>gr\u00e1fico <\/b><\/span><\/span><\/span>observamos que o <\/b><\/span><\/span><\/span>indiv\u00edduo A consegue ouvir melhor que o indiv\u00edduo B sons <\/b><\/span><\/span><\/span>com <\/b><\/span><\/span><\/span>freq\u00fc\u00eancias compreendidas entre 20Hz e 200Hz <\/b><\/span><\/span><\/span>porque a <\/b><\/span><\/span><\/span>curva de seu n\u00edvel sonoro <\/b><\/span><\/span><\/span>(curva tracejada) <\/b><\/span><\/span><\/span>est\u00e1 mais baixa <\/b><\/span><\/span><\/span>(mais pr\u00f3xima do <\/b><\/span><\/span><\/span>limiar de audi\u00e7\u00e3o que \u00e9 0 dB<\/b><\/span><\/span><\/span>) ou,<\/b><\/span><\/span><\/span> o <\/b><\/span><\/span><\/span>indiv\u00edduo A <\/b><\/span><\/span><\/span>consegue ouvir <\/b><\/span><\/span><\/span>melhor que o indiv\u00edduo B <\/b><\/span><\/span><\/span>quando o <\/b><\/span><\/span><\/span>n\u00edvel sonoro, necess\u00e1rio para A ouvir, for menor que o de B. <\/b><\/span><\/span><\/span>Portanto, <\/b><\/span><\/span><\/span>A consegue ouvir melhor que <\/b><\/span><\/span><\/span>B na <\/b><\/span><\/span><\/span>faixa de frequ\u00eancia de 20 Hz a 200 Hz.<\/b><\/span><\/span><\/span><\/p>\n

b<\/b><\/span><\/span><\/span>) <\/b><\/span><\/span>Pelo <\/b><\/span><\/span><\/span>enunciado, o n\u00edvel sonoro m\u00ednimo<\/b><\/span><\/span><\/span> que causa <\/b><\/span><\/span><\/span>dor em um ser humano \u00e9 de 120 dB<\/b><\/span><\/span><\/span>, o que corresponde a uma <\/b><\/span><\/span><\/span>intensidade NS = 120 dB\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0\u00a0120 = 10log(I\/Io)\u00a0 \"\"\u00a0 12 = log(I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 —\u00a0 10<\/b><\/span><\/span><\/span>12<\/b><\/span><\/span><\/sup><\/span> = <\/b><\/span><\/span><\/span><\/p>\n

I\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 I = 10<\/b><\/span><\/span><\/span>0<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>I = 1 W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>O ru\u00eddo atinge o ouvinte com um NS<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span> = 10 dB \"\" pelo gr\u00e1fico<\/b><\/span><\/span><\/span>, quando f=100Hz \"\" NS<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>= 40dB. Assim, o <\/b><\/span><\/span><\/span>n\u00edvel sonoro deve passar de 10dB para 40dB.<\/b><\/span><\/span><\/span><\/p>\n

NS<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 10 dB\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 10 = 10log(I<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)\u00a0 \"\"\u00a0 1 = log(I<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 \"\"\u00a0 10<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sup><\/span>= I<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>I<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 10<\/b><\/span><\/span><\/span>-11<\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

NS<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>= 40 dB<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 40 = 10log(I<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/I<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)\u00a0 \"\"\u00a0\u00a0 4 = log(I<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>)\u00a0 \"\"\u00a0\u00a0 10<\/b><\/span><\/span><\/span>4 <\/b><\/span><\/span><\/sup><\/span>= I<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>I<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>= 10<\/b><\/span><\/span><\/span>-8 <\/b><\/span><\/span><\/sup><\/span>W\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

I<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/I<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\/10<\/b><\/span><\/span><\/span>-11<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 I<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/I<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 10<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>I<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>= 10<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>I<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0 \"\"\u00a0 deve ser ampliada de 1.000 vezes.<\/b><\/span><\/span><\/span><\/p>\n

04-(UFC)<\/b><\/span><\/span><\/span> Sonoridade ou intensidade auditiva <\/b><\/span><\/span><\/span>\u00e9 a <\/b><\/span><\/span><\/span>qualidade do som que permite ao ou<\/b><\/span><\/span><\/span>vinte distinguir um <\/b><\/span><\/span><\/span>som fraco (pequena intensidade) de um som forte (grande intensidade). <\/b><\/span><\/span><\/span>\"\"<\/p>\n

Em um <\/b><\/span><\/span><\/span>jogo de futebol, <\/b><\/span><\/span><\/span>um <\/b><\/span><\/span><\/span>torcedor grita “gol” <\/b><\/span><\/span><\/span>com uma <\/b><\/span><\/span><\/span>sonoridade de 40 dB.<\/b><\/span><\/span><\/span><\/p>\n

Qual ser\u00e1 a<\/b><\/span><\/span><\/span> sonoridade (em dB), <\/b><\/span><\/span><\/span>se <\/b><\/span><\/span><\/span>10 000 torcedores gritam “gol” ao mesmo tempo e com a mesma intensidade?<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>n\u00edvel sonoro total de n fontes id\u00eanticas <\/b><\/span><\/span><\/span>\u00e9 dado por <\/b><\/span><\/span><\/span>L(t) = 10.log(n) + L, onde L \u00e9 o n\u00edvel sonoro de apenas uma fonte.<\/b><\/span><\/span><\/span><\/p>\n

Assim \"\"<\/b><\/span><\/span><\/span> <\/b>NS(t) = 10.log(10 000) + 40 \"\"<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span>NS(t) = 10log10<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sup><\/span>\u00a0+ 40\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 NS(t) = 10.4log10 + 40 \"\"<\/b><\/span><\/span><\/span><\/p>\n

NS(t) =10.4.1 + 40\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>NS(t) = 80 dB.<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Confira os exerc\u00edcios<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Qualidades fisiol\u00f3gicas do som Produ\u00e7\u00e3o e percep\u00e7\u00e3o de ondas sonoras Quando uma fonte sonora (l\u00e2mina, corda, membrana, etc.) \u00e9 colocada para vibrar, ela provoca em toda sua volta, no meio que a envolve (normalmente o ar), ondas mec\u00e2nicas longitudinais que, por meio de sucessivas compress\u00f5es e rarefa\u00e7\u00f5es das part\u00edculas desse meio, viajam em todas as dire\u00e7\u00f5es (meio tridimensional), formando assim,<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2325,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-2366","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2366","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/comments?post=2366"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2366\/revisions"}],"predecessor-version":[{"id":2376,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2366\/revisions\/2376"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2325"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2366"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}