{"id":4422,"date":"2022-01-12T12:31:21","date_gmt":"2022-01-12T03:31:21","guid":{"rendered":"https:\/\/www.skyer9.pe.kr\/wordpress\/?p=4422"},"modified":"2022-01-14T22:28:39","modified_gmt":"2022-01-14T13:28:39","slug":"%ed%93%a8%eb%a6%ac%ec%97%90%eb%b3%80%ed%99%98","status":"publish","type":"post","link":"https:\/\/www.skyer9.pe.kr\/wordpress\/?p=4422","title":{"rendered":"\ud4e8\ub9ac\uc5d0 \ubcc0\ud658(Fourier Transform, \ud478\ub9ac\uc5d0 \ubcc0\ud658)"},"content":{"rendered":"<h1>\ud4e8\ub9ac\uc5d0 \ubcc0\ud658(Fourier Transform, \ud478\ub9ac\uc5d0 \ubcc0\ud658)<\/h1>\n<p>\ud478\ub9ac\uc5d0 \ubcc0\ud658\uc774 \ub9de\ub294 \ub9d0\uc774\ub77c\uace0 \ud55c\ub2e4.<br \/>\n\ud558\uc9c0\ub9cc \uc778\ud130\ub137\uc744 \uac80\uc0c9\ud558\uba74 <code>\ud4e8\ub9ac\uc5d0 \ubcc0\ud658<\/code> \uc774 \ub354 \ub9ce\uc740 \uac80\uc0c9\uacb0\uacfc\ub97c \ub0b4\uc900\ub2e4.<\/p>\n<p><a href=\"http:\/\/www.incodom.kr\/%ED%91%B8%EB%A6%AC%EC%97%90_%EB%B3%80%ED%99%98\">\ucc38\uc870 : \uc5ec\uae30 \ubb38\uc11c\uac00 \uc544\uc8fc \uc88b\ub2e4<\/a><\/p>\n<p><a href=\"https:\/\/m.blog.naver.com\/PostView.naver?blogId=choi_s_h&amp;logNo=222128246691&amp;proxyReferer=\">\ucc38\uc870 : \uc5ec\uae30 \ubb38\uc11c\ub3c4 \uc544\uc8fc \uc88b\ub2e4<\/a><\/p>\n<p><a href=\"https:\/\/spacebike.tistory.com\/6\">\ucc38\uc870 : \uc5ec\uae30\ub3c4 \uc544\uc8fc \uc88b\ub2e4<\/a><\/p>\n<p><a href=\"https:\/\/darkpgmr.tistory.com\/m\/171\">\ucc38\uc870<\/a><\/p>\n<h2>\ubb50\uc5d0 \uc4f0\ub294 \ubb3c\uac74\uc778\uac00?<\/h2>\n<p>\ub0a8\uc790, \uc5ec\uc790\uac00 \ub3d9\uc2dc\uc5d0 \ub5a0\ub4e4\uc5b4 \ub300\uba74 \uc18c\ub9ac\uac00 \uc11e\uc774\uac8c \ub41c\ub2e4.<br \/>\n\uc774\ub7f0 \uacbd\uc6b0 \ub0a8\uc790\uc758 \uc18c\ub9ac\ub9cc \ucd94\ucd9c\ud558\uace0 \uc2f6\ub2e4\uba74 \uc5b4\ub5bb\uac8c \ud560 \uc218 \uc788\uc744\uae4c?<\/p>\n<p>\uc804\ud30c\uc758 \uacbd\uc6b0\ub3c4 \uc6d0\ubcf8\uc804\ud30c, \uc7a1\uc2e0\ud638(white noise), \ub4a4\ub2a6\uac8c \ub3c4\ucc29\ud55c \uc6d0\ubcf8\uc804\ud30c\uac00 \uc11e\uc5ec \uc788\ub294 \uc0c1\ud0dc\uc774\ub2e4.<br \/>\n\uc774 \ub54c \uc6d0\ubcf8 \uc804\ud30c\ub9cc \uc5bb\uc73c\ub824\uba74 \uc5b4\ub5bb\uac8c \ud560 \uac83\uc778\uac00?<\/p>\n<p>\uc774\ub7f0 \uc11e\uc5ec \uc788\ub294 \uc0c1\ud0dc\uc758 \ud30c\ub3d9(\uc18c\ub9ac \ub610\ub294 \uc804\ud30c)\ub97c \ubd84\ub9ac\ud574 \ub0b4\ub294 \uae30\ub2a5\uc744 \ud558\ub294 \uac83\uc774 \ud4e8\ub9ac\uc5d0 \ubcc0\ud658\uc774\ub2e4.<\/p>\n<h2>\ud478\ub9ac\uc5d0 \ubcc0\ud658 \uc804\uacc4<\/h2>\n<ul>\n<li>\n<p>\ud30c\ub3d9\uc740 sin, cos \uc73c\ub85c \ub098\ud0c0\ub0bc \uc218 \uc788\ub2e4.<\/p>\n<\/li>\n<li>\n<p>\ubaa8\ub4e0 \ud30c\ub3d9\uc740 sin, cos\uc758 \ud569\uc73c\ub85c \uc774\ub8e8\uc5b4\uc838 \uc788\uc73c\uba70 \uc5ed\uc73c\ub85c \ud30c\ub3d9\uc744 sin, cos\uc73c\ub85c \ub098\ud0c0\ub0bc \uc218 \uc788\ub2e4<br \/>\n(\ud478\ub9ac\uc5d0 \uae09\uc218).<\/p>\n<\/li>\n<li>\n<p>\ud478\ub9ac\uc5d0 \uae09\uc218\uc5d0\uc11c \uacc4\uc218\uc640 \uc8fc\ud30c\uc218\ub97c \uad6c\ud55c\ub2e4.<\/p>\n<\/li>\n<li>\n<p>\uc774 \uacc4\uc218\uc640 \uc8fc\ud30c\uc218\uac00 \ud478\ub9ac\uc5d0 \ubcc0\ud658\uc774\ub2e4.<\/p>\n<\/li>\n<\/ul>\n<h2>\uad6c\ud604<\/h2>\n<p>\uc77c\ub2e8 sox \ub97c \uc774\uc6a9\ud574 wav \ud30c\uc77c\uc744 \uc0dd\uc131\ud55c\ub2e4.<\/p>\n<p>\uc0ac\ub78c\uc758 \uac00\uccad\uc8fc\ud30c\uc218 \ub54c\ubb38\uc5d0 \ub4e4\uc744 \uc218 \uc788\ub294 \uc8fc\ud30c\uc218\ub294 300Hz, 10000Hz \ubfd0\uc774\ub2e4.<\/p>\n<pre><code class=\"language-bash\">sox --null -r 22050 sine_20.wav synth 3 sine 20 #20Hz\naplay sine_20.wav\n\nsox --null -r 22050 sine_300.wav synth 3 sine 300 #300Hz\naplay sine_300.wav\n\nsox --null -r 22050 sine_10000.wav synth 3 sine 10000 #10,000Hz\naplay sine_10000.wav\n\nsox --null -r 22050 sine_30000.wav synth 3 sine 30000 #30,000Hz\naplay sine_30000.wav\n\nsox --combine mix --volume 0.5 sine_300.wav --volume 0.5 sine_10000.wav sine_mix.wav\naplay sine_mix.wav<\/code><\/pre>\n<pre><code class=\"language-python\">#!\/usr\/bin\/python3\n\nimport os\nimport glob\n\nimport scipy\nimport scipy.io.wavfile\nfrom scipy import fftpack\nimport matplotlib.pyplot as plt\nimport numpy as np\n\ndef plot_wav_fft(wav_filename, desc=None, trans=False):\n    plt.clf()\n    plt.figure(num=None, figsize=(6, 4))\n    sample_rate, X = scipy.io.wavfile.read(wav_filename)\n    spectrum = fftpack.fft(X)\n    freq = fftpack.fftfreq(len(X), d=1.0 \/ sample_rate)\n\n    plt.subplot(211)\n    num_samples = 300.0\n    plt.xlim(0, num_samples \/ sample_rate)\n    plt.xlabel(&quot;time [s]&quot;)\n    plt.title(desc or wav_filename)\n    plt.plot(np.arange(num_samples) \/ sample_rate, X[:int(num_samples)])\n    plt.grid(True)\n\n    if trans:\n        plt.subplot(212)\n        plt.xlim(0, 5000)\n        plt.xlabel(&quot;frequency [Hz]&quot;)\n        plt.xticks(np.arange(5) * 4000)\n        if desc:\n            desc = desc.strip()\n            fft_desc = desc[0].lower() + desc[1:]\n        else:\n            fft_desc = wav_filename\n        plt.title(&quot;FFT of %s&quot; % fft_desc)\n        plt.plot(freq, abs(spectrum), linewidth=2)\n        plt.grid(True)\n        plt.tight_layout()\n\n    rel_filename = os.path.split(wav_filename)[1]\n    plt.savefig(&quot;%s_wav_fft.png&quot; % os.path.splitext(rel_filename)[0],\n                bbox_inches=&#039;tight&#039;)\n\n    plt.show()\n\ndef plot_wav_fft_demo():\n    plot_wav_fft(&quot;sine_300.wav&quot;)\n    plot_wav_fft(&quot;sine_10000.wav&quot;)\n    plot_wav_fft(&quot;sine_mix.wav&quot;)\n    plot_wav_fft(&quot;sine_mix.wav&quot;, &quot;sine_mix&quot;, True)\n\nplot_wav_fft_demo()<\/code><\/pre>\n<p>\uc704 \ud30c\uc77c\uc744 \uc2e4\ud589\uc2dc\ud0a4\uba74 \uc544\ub798\uc640 \uac19\uc774 \uc8fc\ud30c\uc218 \uadf8\ub798\ud504\uac00 \uadf8\ub824\uc9c4\ub2e4.<\/p>\n<p>300Hz<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.skyer9.pe.kr\/wordpress\/wp-content\/uploads\/2022\/01\/2022-01-13-01.png\" alt=\"\" \/><\/p>\n<p>10000Hz<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.skyer9.pe.kr\/wordpress\/wp-content\/uploads\/2022\/01\/2022-01-13-02.png\" alt=\"\" \/><\/p>\n<p>300Hz + 10000Hz<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.skyer9.pe.kr\/wordpress\/wp-content\/uploads\/2022\/01\/2022-01-13-03.png\" alt=\"\" \/><\/p>\n<p>\ub9c8\uc9c0\ub9c9\uc73c\ub85c \uc694\uc0c1\ud55c \uadf8\ub798\ud504\uac00 \ub098\uc654\ub2e4.<\/p>\n<p>\uc774\uac83\uc774 \ud4e8\ub9ac\uc5d0 \ubcc0\ud658\uc774\ub2e4.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.skyer9.pe.kr\/wordpress\/wp-content\/uploads\/2022\/01\/2022-01-13-04.png\" alt=\"\" \/><\/p>\n<p>\uc704 \ub450 \uadf8\ub798\ud504\uc911 \uc544\ub798 \uadf8\ub798\ud504\uc758 X\ucd95\uc744 \uac00\ub9cc\ud788 \ubcf4\uba74,<br \/>\n300Hz, 10000Hz \ucc98\ub7fc \ubcf4\uc774\uc9c0 \uc54a\ub294\uac00?<\/p>\n<p>\uc880 \ub354 \ud655\uc2e4\ud788 \ud558\uae30 \uc704\ud574,<br \/>\n200Hz \uc640 300Hz \ud30c\uc77c\uc744 \uc0dd\uc131\ud558\uace0,<br \/>\n\ubcfc\ub968\ub3c4 0.3, 0.7 \ub85c \ub2e4\ub974\uac8c \uc785\ub825\ud558\uace0 \ub2e4\uc2dc \ub3d9\uc77c\ud558\uac8c \uc2e4\ud589\uc2dc\ucf1c \ubcf4\uc790.<\/p>\n<pre><code class=\"language-bash\">sox --null -r 22050 sine_200.wav synth 3 sine 200\nsox --null -r 22050 sine_300.wav synth 3 sine 300\nsox --combine mix --volume 0.3 sine_200.wav --volume 0.7 sine_300.wav sine_mix_200_300.wav<\/code><\/pre>\n<pre><code class=\"language-python\"># ......................\n    if trans:\n        plt.subplot(212)\n        plt.xlim(0, 20)\n        plt.xlabel(&quot;frequency [Hz]&quot;)\n        plt.xticks(np.arange(5) * 100)\n# ......................\n\ndef plot_wav_fft_demo():\n    # plot_wav_fft(&quot;sine_200.wav&quot;)\n    # plot_wav_fft(&quot;sine_300.wav&quot;)\n    # plot_wav_fft(&quot;sine_mix_200_300.wav&quot;)\n    plot_wav_fft(&quot;sine_mix_200_300.wav&quot;, &quot;sine_mix&quot;, True)\n\nplot_wav_fft_demo()<\/code><\/pre>\n<p><img decoding=\"async\" src=\"https:\/\/www.skyer9.pe.kr\/wordpress\/wp-content\/uploads\/2022\/01\/2022-01-13-05.png\" alt=\"\" \/><\/p>\n<h2>\ud478\ub9ac\uc5d0 \uae09\uc218(Fourier series)<\/h2>\n<blockquote>\n<p>\ud478\ub9ac\uc5d0\uc758 \ubc1c\uacac : \ub3d9\uc77c\ud55c \ud615\ud0dc\ub97c \ubc18\ubcf5\ud558\ub294\ud30c\ub3d9\uc740,<br \/>\n\uc544\ubb34\ub9ac \ubcf5\uc7a1\ud55c \uac83\uc774\ub77c\ub3c4 \ub2e8\uc21c\ud55c \ud30c\ub3d9\uc758 \uc870\ud569\uc774\ub2e4.<\/p>\n<\/blockquote>\n<p>\uc704\uc5d0\uc11c \ubcf4\uc558\ub4ef\uc774 200Hz + 300Hz \uc758 \uc8fc\ud30c\uc218\uac00 \ubcf5\uc7a1\ud574 \ubcf4\uc774\uc9c0\ub9cc,<br \/>\n\uacb0\uad6d \ub2e8\uc21c\ud55c \ud30c\ub3d9 \ub450\uac00\uc9c0\uac00 \uc11e\uc5ec\uc11c \ub098\uc624\ub294 \uac83\uacfc \uac19\ub2e4.<\/p>\n<p>\uc774\uac83\uc744 \uc218\uc2dd\ud654 \ud574\ubcf4\uc790.<\/p>\n<pre><code class=\"language-bash\">(\ubcf5\uc7a1\ud55c \ud30c\ub3d9) = (\ub2e8\uc21c\ud55c \ud30c\ub3d9 1)  +  (\ub2e8\uc21c\ud55c \ud30c\ub3d9 2)  +  (\ub2e8\uc21c\ud55c \ud30c\ub3d9 3)  +  ...<\/code><\/pre>\n<p>\uc774\ub97c \uc218\uc2dd\ud654\ud558\uba74 \uc544\ub798\uc640 \uac19\uc740 \uacf5\uc2dd\uc774 \ub098\uc628\ub2e4.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.skyer9.pe.kr\/wordpress\/wp-content\/uploads\/2022\/01\/2022-01-13-05-1.png\" alt=\"\" \/><\/p>\n<h2>\ud4e8\ub9ac\uc5d0 \ubcc0\ud658<\/h2>\n<p>\ud4e8\ub9ac\uc5d0 \uae09\uc218\uac00 \uc8fc\uae30\ub97c \uac00\uc9c0\ub294 \ud30c\ub3d9\uc758 \uc8fc\ud30c\uc218 \uc694\uc18c\ub97c \ucc3e\ub294 \uac83\uc5d0 \ube44\ud574,<br \/>\n\ud4e8\ub9ac\uc5d0 \ubcc0\ud658\uc740 \ud604\uc7ac \ubcf4\uc774\ub294 \ud30c\ub3d9\uc774 \ubb34\uc2a8 \uc8fc\ud30c\uc218\ub85c \uad6c\uc131\ub418\uc5b4 \uc788\ub294\uac00\ub97c \ucc3e\ub294\ub2e4.<\/p>\n<p>\uc774 \uc544\uc774\ub514\uc5b4\uac00 \uc5c4\uccad\ub09c \uacb0\uacfc\ub97c \ub9cc\ub4e0\ub2e4.<\/p>\n<h2>\ud4e8\ub9ac\uc5d0 \ubcc0\ud658\uc758 \uc751\uc6a9<\/h2>\n<p>\uc18c\ub9ac \uc601\uc5ed\uc5d0 \ub300\ud574\uc11c\ub294 mp3, \uc601\uc0c1 \uc601\uc5ed\uc5d0\uc11c\ub294 mpeg\/jpeg \ub4f1.<br \/>\n\uc815\ub9d0 \ub9ce\uc740 \uacf3\uc5d0\uc11c \uc4f0\uc774\uace0 \uc788\ub2e4.<\/p>\n<p>\ud4e8\ub9ac\uc5d0 \uae09\uc218\uac00 \uc8fc\uae30\ub97c \uac00\uc9c0\ub294 \ud30c\ub3d9\uc758 \uc8fc\ud30c\uc218\ub97c \ucc3e\ub294\uac74\ub370&#8230;<br \/>\n\uadf8\ub7f0\uac70 \ub2e4 \ud544\uc694\uc5c6\uace0 \uadf8\ub0e5 \uc9c0\uae08\uc758 \ud30c\ub3d9\uc774 \ubb34\uc2a8 \uc8fc\ud30c\uc218\ub85c \uc774\ub8e8\uc5b4 \uc84c\ub0d0\ub9cc \ucc3e\ub294 \uac1c\ub150\uc774\ub2e4.<br \/>\n\ucd5c\uadfc 0.1\ucd08\uc758 \ub370\uc774\ud0c0\uac00 \ubcf5\uc7a1\ud55c\ub370&#8230;<br \/>\n\uc774\uac78 \ud4e8\ub9ac\uc5d0 \ubcc0\ud658\uc73c\ub85c \ubc14\uafb8\uba74 \ub370\uc774\ud0c0\uac00 \uc5c4\uccad \uc904\uc5b4\ub4dc\ub294 \ub290\ub08c\uc774\ub784\uae4c&#8230;<\/p>\n<h2>\ud4e8\ub9ac\uc5d0 \ubcc0\ud658 = \uc804\ud30c \uc138\uacc4\uc5d0\uc11c \uc54c\ud30c\uc774\uc790 \uc624\uba54\uac00<\/h2>\n<p>\uc544\uc9c1 \uacf5\ubd80\uac00 \ubd80\uc871\ud558\uc9c0\ub9cc,<br \/>\n\uc8fc\ud30c\uc218\ub97c \ubd84\ub9ac\ud574 \ub0b4\uace0 \uc2e0\ud638\uc758 \uac15\ub3c4\ub97c \ubd84\ub9ac\ud574 \ub0b4\ub294\uac78 \ubcf4\uba74,<br \/>\n\uc804\ud30c\uc5d0 \ub300\ud574 \uc5bc\ub9c8\ub098 \ud4e8\ub9ac\uc5d0 \ubcc0\ud658\uc744 \uc368\uba39\uc73c\ub824 \ud588\uc744\uc9c0 \uc54a\ubd10\ub3c4 \ube44\ub514\uc624\uace0,<br \/>\n\ub098\ub3c4 \uadf8\ub7ac\uc744\uac70\uace0,<br \/>\n\uc2e4\uc81c\ub85c\ub3c4 \uadf8\ub7f4\uac83 \uac19\ub2e4.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\ud4e8\ub9ac\uc5d0 \ubcc0\ud658(Fourier Transform, \ud478\ub9ac\uc5d0 \ubcc0\ud658) \ud478\ub9ac\uc5d0 \ubcc0\ud658\uc774 \ub9de\ub294 \ub9d0\uc774\ub77c\uace0 \ud55c\ub2e4. \ud558\uc9c0\ub9cc \uc778\ud130\ub137\uc744 \uac80\uc0c9\ud558\uba74 \ud4e8\ub9ac\uc5d0 \ubcc0\ud658 \uc774 \ub354 \ub9ce\uc740 \uac80\uc0c9\uacb0\uacfc\ub97c \ub0b4\uc900\ub2e4. \ucc38\uc870 : \uc5ec\uae30 \ubb38\uc11c\uac00 \uc544\uc8fc \uc88b\ub2e4 \ucc38\uc870 : \uc5ec\uae30 \ubb38\uc11c\ub3c4 \uc544\uc8fc \uc88b\ub2e4 \ucc38\uc870 : \uc5ec\uae30\ub3c4 \uc544\uc8fc \uc88b\ub2e4 \ucc38\uc870 \ubb50\uc5d0 \uc4f0\ub294 \ubb3c\uac74\uc778\uac00? \ub0a8\uc790, \uc5ec\uc790\uac00 \ub3d9\uc2dc\uc5d0 \ub5a0\ub4e4\uc5b4 \ub300\uba74 \uc18c\ub9ac\uac00 \uc11e\uc774\uac8c \ub41c\ub2e4. \uc774\ub7f0 \uacbd\uc6b0 \ub0a8\uc790\uc758 \uc18c\ub9ac\ub9cc \ucd94\ucd9c\ud558\uace0 \uc2f6\ub2e4\uba74\u2026 <span class=\"read-more\"><a href=\"https:\/\/www.skyer9.pe.kr\/wordpress\/?p=4422\">Read More &raquo;<\/a><\/span><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35,1],"tags":[],"class_list":["post-4422","post","type-post","status-publish","format-standard","hentry","category-rf-sdr","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/4422","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4422"}],"version-history":[{"count":27,"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/4422\/revisions"}],"predecessor-version":[{"id":4456,"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/4422\/revisions\/4456"}],"wp:attachment":[{"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4422"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4422"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.skyer9.pe.kr\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4422"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}