仓库源文，站点原文

title: 声音的滤波 categories:

• JavaScript
• 前端杂烩
• 网络交互 tags:
• tech
• cnblogs
• webaudio warning: true date: 2014-02-28 01:57:00 fromUrl: http://www.cnblogs.com/hustskyking/archive/2014/02/28/webAudio-filter.html from: 博客园

enum BiquadFilterType {
    "lowpass",
    "highpass",
    "bandpass",
    "lowshelf",
    "highshelf",
    "peaking",
    "notch",
    "allpass"
};

attribute BiquadFilterType type;
readonly attribute AudioParam frequency; // in Hertz
readonly attribute AudioParam detune; // in Cents
readonly attribute AudioParam Q; // Quality factor
readonly attribute AudioParam gain; // in Decibels

void getFrequencyResponse(Float32Array frequencyHz,
                          Float32Array magResponse,
                          Float32Array phaseResponse);

};

// 初始化为低通滤波
var filter = context.createBiquadFilter("lowpass");

var filter = context.createBiquadFilter();
// 设置为低通滤波
filter.type = filter.LOWPASS;
// 只允许频率小于 800Hz 的音频信号通过
filter.frequency.value = 800;

var AudioContext = AudioContext || webkitAudioContext;
var context = new AudioContext;
//创建节点
var audio = new Audio("http://qianduannotes.duapp.com/file/SuperMario.mp3");
audio.loop = true;
var media = context.createMediaElementSource(audio);
var filter = context.createBiquadFilter();
filter.type=filter.LOWPASS;
filter.frequency.value=800;
//连接：media → filter → destination
media.connect(filter);
filter.connect(context.destination);audio.play();

filter.frequency.value = volume.value * volume.value;

<p>线性变化可能不太明显，所以改成了平方变化。</p>

<h3>二、小结</h3>

<p>滤波在通信中一个重要的意义是减少数据传输量，节约频带，提高传送效率，在硬件设备还未跟上语音通信的 web环境中，这个操作是十分有意义的！</p>

<p>本节重点是介绍 BiquadFilterNode 在 AudioContext 环境中的使用，比较简单。</p>

<h3>三、参考资料</h3>