音頻均衡器EQ

{"type":"doc","content":[{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"概述 ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" EQ（Equaliser）爲音頻均衡器，通過對聲音某一個或多個頻段進行增益或者衰減，其他頻段保持不變從而達到調整音色的目的。音頻均衡器在各個音樂app中，各個RTC廠商中都可以設置。以聲網的RTC的demo爲例，圖中紅色的部分就是音頻均衡器。：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/b4/b41efef0752fed33a40fdaaa63ca45d3.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"人聲對各個頻段的感受","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先我們來了解一下各個頻段對人聲的影響。人耳可分辨的聲音頻率大約是在20Hz~20kHz，因此調音臺中的四段均衡器把其分爲的4個頻段，根據德國柏林音樂研究所資料介紹，它們是： ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"•  HF（高頻）：6kHz-16kHz，影響音色的表現力、解析力。 ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"•  MID HF（中高頻）：600Hz-6kHz，影響音色的明亮度、清晰度。 ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"•  MID LF（中低頻）：200Hz-600Hz，影響音色和力茺和結實度。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"•  LF（低頻）：20Hz-200Hz，影響音色的混厚度和豐滿度。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 下面是關於調音的一些知識（來源於","attrs":{}},{"type":"link","attrs":{"href":"https://wenku.baidu.com/view/959e8ce328ea81c758f57855.html","title":"","type":null},"content":[{"type":"text","text":"EQ各頻段的基本知識-調音必看","attrs":{}}]},{"type":"text","text":"），我也沒有自己調過，拿出來讓大家對各個頻段有個感性的認識","attrs":{}}]},{"type":"numberedlist","attrs":{"start":1,"normalizeStart":1},"content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"[20－60Hz]影響音色的空間感","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"[60-100Hz]影響聲音的混厚感，是低音的基音區。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":"[80－160Hz]主要表現音樂的厚實感，音響在這部分重放效果好的話，會感到音樂厚實、有底氣。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","text":"[150－300Hz]影響聲音的力度，尤其是男音的力度。這段頻率是男聲聲音的低頻基音頻率，同時也是樂音中和絃的根音頻率。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":5,"align":null,"origin":null},"content":[{"type":"text","text":"[300－500Hz]表現人聲的（唱歌、朗誦），這個頻段上可以表現人聲的厚度和力度，好則人聲明亮、清晰，否則單薄、混濁。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":6,"align":null,"origin":null},"content":[{"type":"text","text":"[800Hz]影響音色的力度。如果這個頻率豐滿，音色會顯得強勁有力;如果不足，音色將會顯得鬆弛","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":7,"align":null,"origin":null},"content":[{"type":"text","text":"[1kHz]是音響器材測試的標準參考頻率，通常在音響器材中給出的參數是在1kHz下測試。這是人耳最爲敏感的頻率。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":8,"align":null,"origin":null},"content":[{"type":"text","text":"[1.2kHz]可以適當多一點，不宜太多，可以提高聲音的明亮度，過多會使聲音發硬。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":9,"align":null,"origin":null},"content":[{"type":"text","text":"[2k-4kHz]穿透力很強。人耳耳腔的諧振頻率是1∽4KHz，所以人耳對這個頻率也是非常敏感的。2-4kHz對聲音的亮度影響很大，這段聲音一般不宜衰減。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":10,"align":null,"origin":null},"content":[{"type":"text","text":"[4k－8kHz]這段頻率最影響語音的清晰度、明亮度、如果這頻率成分缺少，音色則變得平平淡淡;如果這段頻率成分過多，音色則變得尖銳，人聲可能出現齒音。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":11,"align":null,"origin":null},"content":[{"type":"text","text":"[8k-12kHz]這段是音樂的高音區，對音響的高頻表現感覺最爲敏感。適當突出（一點即可）對音響的的層次和色彩有較大幫助，也會讓人感到高音豐富。但是，太多的話會增加背景噪聲，同時也會讓人感到聲音發尖、發毛。如果這段缺乏的話，聲音將缺乏感染力和活力。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":12,"align":null,"origin":null},"content":[{"type":"text","text":"[12k－16kHz]能夠影響整體的色彩感，這段過於黯淡會導致樂器失去個性，過多則會產生毛刺感。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":13,"align":null,"origin":null},"content":[{"type":"text","text":"[16k－20kHz]可能很多人都聽不到，聽不到並不意味着器材無法回放，只有很少人可以聽到20kHz。這段頻率可以影響高頻的亮度，以及整體的空間感，過少會讓人覺得有點悶，太多則會產生飄忽感，容易產生聽覺疲勞。電子合聲、古箏鋼琴等樂器的泛音多表現於此。","attrs":{}}]}]}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"EQ參數設置","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" EQ的設計原理不復雜，但是如何調節各個波段的增益保持聲音動聽這是一大難點。EQ通常使用濾波器來對各個頻段濾波來實現。通常我們會把EQ設置爲10個頻段，每個頻段有中間頻率，截止頻率，起始頻率。在書籍《Audio Effects》有如下表，其中左邊代表倍頻，右邊代表1/3倍頻：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/fc/fc2fb49629195f8e9a8fc5c68a79f086.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 根據以上的介紹，我們知道EQ中最重要的參數包括：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"1）進行增益的中心頻率：f0","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2) 當前頻段要進行的增益：G Gain增益可以爲正爲負","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"3）設定進行增益或衰減頻段寬度的參數：Q Quantize，Q越小，頻段越寬；反之，頻段越窄。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 確定好EQ中需要的參數後，下一步就是設計對各個頻段進行增益or衰減的濾波器，濾波器一般使用IIR濾波器，原始數據經過音頻濾波後便可達到美聲的效果。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"濾波器","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 濾波器常見的有低通、高通、帶通濾波器。這些濾波器都有一個共同的點，理想情況下，在濾波器截止頻率範圍以外，增益基本爲0。而EQ需要對聲音某一個或多個頻段進行增益或者衰減，其他頻段保持不變從而達到調整音色的目的。因此，理想情況下，濾波器截止頻率範圍以外，增益基本爲1。因此，EQ中使用的濾波器爲lowself，highself，peak濾波器。下面詳細介紹下這3種濾波器。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"lowself濾波器","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"lowself濾波器是低通濾波器的一個變形版本，需設置截止頻率外增益爲1。因此，lowshelf 濾波器可以認爲是低通濾波器在截止頻率外並聯一個直通信號。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"lowself濾波器的增益曲線爲：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/d0/d0151a88bf28fc5363f28c69f3c9b32c.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一階lowself濾波器的傳輸函數表示爲：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/56/565b8a464553304776458d4f86df69cd.png","alt":null,"title":"","style":[{"key":"width","value":"50%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其中A(z)是一個一階全通濾波器。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/51/5162b1291deed8bea3d05659032cf72d.png","alt":null,"title":"","style":[{"key":"width","value":"50%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"highself濾波器","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"highself濾波器與lowself的設計是一樣的。只需要將Z變化爲1/Z即可。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"highself濾波器的增益曲線爲：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/b8/b89de1d5553c663a40deeecbbc2ee8ee.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"peak濾波器","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"peak濾波器是帶通濾波器的變形。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"濾波器的增益曲線爲：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/5d/5d8a62275688b480b330ef8e9c7bfbac.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一階peak濾波器設計爲","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/32/32183c96ab539bac90973d3d5568254f.png","alt":null,"title":"","style":[{"key":"width","value":"50%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其中A2(z)爲一個二階全通濾波器","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/0e/0e62383bc3dbb5995363850d15da0ca3.png","alt":null,"title":"","style":[{"key":"width","value":"50%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏我對各個濾波器的傳輸函數介紹的比較簡易：詳細的可以看","attrs":{}},{"type":"link","attrs":{"href":"https://blog.csdn.net/golfbears/article/details/86674390","title":null,"type":null},"content":[{"type":"text","text":"一階shelf IIR數字濾波器的設計和實現","attrs":{}}]},{"type":"text","text":"和","attrs":{}},{"type":"link","attrs":{"href":"https://blog.csdn.net/golfbears/article/details/86702159?utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-6.control&dist_request_id=1331645.147.16183128961363651&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-6.control","title":null,"type":null},"content":[{"type":"text","text":"IIR peaking filter探祕","attrs":{}}]},{"type":"text","text":"。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 對於EQ各個頻段使用濾波器時，第一個頻段需要使用lowshelf filter，最後一個頻段使用highshelf filter，其餘頻段使用peak filter","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"濾波器實現","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"濾波器使用二階的IIR濾波器，可以表示爲","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"頻域行爲:","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"\t\tb0 + b1*z^-1 + b2*z^-2","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"H(z) = ------------------------ ","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" a0 + a1*z^-1 + a2*z^-2","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"時域形式爲：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" y[n] = (b0/a0)*x[n] + (b1/a0)*x[n-1] + (b2/a0)*x[n-2]- (a1/a0)*y[n-1] - (a2/a0)*y[n-2]","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"求解濾波器可以使用Audio_EQ_CookBook中的方法，Audio_EQ_CookBook使用雙線性變換法將濾波器從S域轉換到Z域，爲方便示意，下列參數示意都在S域。關於雙線性變換法可以參考：","attrs":{}},{"type":"link","attrs":{"href":"https://zhuanlan.zhihu.com/p/265965580","title":null,"type":null},"content":[{"type":"text","text":"知乎-雙線性變換法","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先設置中間參數 dBgain增益 f0截止頻率","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"A = sqrt( 10^(dBgain/20) )= 10^(dBgain/40)\nw0 = 2*pi*f0/Fs\nalpha = sin(w0)/(2*Q) (case: Q)\n\t = sin(w0)*sinh( ln(2)/2 * BW * w0/sin(w0) ) (case: BW)\n\t = sin(w0)/2 * sqrt( (A + 1/A)*(1/S - 1) + 2 ) (case: S）","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"loweshelf filter設計爲","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"H(s) = A * (s^2 + (sqrt(A)/Q)*s + A)/(A*s^2 + (sqrt(A)/Q)*s + 1)\n\n//計算可得IIR濾波器參數爲： \nb0 = A*( (A+1) - (A-1)*cos(w0) + 2*sqrt(A)*alpha )\nb1 = 2*A*( (A-1) - (A+1)*cos(w0) )\nb2 = A*( (A+1) - (A-1)*cos(w0) - 2*sqrt(A)*alpha )\na0 = (A+1) + (A-1)*cos(w0) + 2*sqrt(A)*alpha\na1 = -2*( (A-1) + (A+1)*cos(w0) )\na2 = (A+1) + (A-1)*cos(w0) - 2*sqrt(A)*alpha","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"highshelf filter設計爲","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"H(s) = A * (A*s^2 + (sqrt(A)/Q)*s + 1)/(s^2 + (sqrt(A)/Q)*s + A)\n \nb0 = A*( (A+1) + (A-1)*cos(w0) + 2*sqrt(A)*alpha )\nb1 = -2*A*( (A-1) + (A+1)*cos(w0) )\nb2 = A*( (A+1) + (A-1)*cos(w0) - 2*sqrt(A)*alpha )\na0 = (A+1) - (A-1)*cos(w0) + 2*sqrt(A)*alpha\na1 = 2*( (A-1) - (A+1)*cos(w0) )\na2 = (A+1) - (A-1)*cos(w0) - 2*sqrt(A)*alpha","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"peak filter設計爲","attrs":{}}]},{"type":"codeblock","attrs":{"lang":"text"},"content":[{"type":"text","text":"H(s) = (s^2 + s*(A/Q) + 1) / (s^2 + s/(A*Q) + 1)\n \nb0 = 1 + alpha*A\nb1 = -2*cos(w0)\nb2 = 1 - alpha*A\na0 = 1 + alpha/A\na1 = -2*cos(w0)\na2 = 1 - alpha/A","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"開源代碼的實現","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"開源音頻編輯軟件audacity實現了EQ，可參照其實現自己的EQ。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"小結","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 本文介紹了音頻EQ及其原理，側重點還是在EQ的濾波器的設計上。EQ的濾波器一般使用IIR濾波器，這樣節省了很多運算複雜度，但是實現IIR濾波器的時候，一定要考慮濾波器的穩定性。關於EQ的代碼剖析，如果有時間，會補上。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"參考","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://blog.csdn.net/golfbears/article/details/86674390","title":null,"type":null},"content":[{"type":"text","text":"一階shelf IIR數字濾波器的設計和實現","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://blog.csdn.net/golfbears/article/details/86702159?utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-6.control&dist_request_id=1331645.147.16183128961363651&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-6.control","title":null,"type":null},"content":[{"type":"text","text":"IIR peaking filter探祕","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://zhuanlan.zhihu.com/p/254910652","title":null,"type":null},"content":[{"type":"text","text":"知乎-均衡器EQ原理及應用","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://zhuanlan.zhihu.com/p/265965580","title":null,"type":null},"content":[{"type":"text","text":"知乎-雙線性變換法","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://my.oschina.net/u/4388335/blog/3321835","title":null,"type":null},"content":[{"type":"text","text":"EQ概念","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"http://iowahills.com/A7ExampleCodePage.html","title":null,"type":null},"content":[{"type":"text","text":"Fir與Iir濾波器設計","attrs":{}}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https://wenku.baidu.com/view/959e8ce328ea81c758f57855.html","title":"","type":null},"content":[{"type":"text","text":"EQ各頻段的基本知識-調音必看","attrs":{}}]}]}]}