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HTML

              
                <header class="header">
    <h1>HTML5 获取当前系统麦克风音量</h1><hr>
</header>

<div class="container">
  <button onclick="beginDetect()">开始检测</button>
  <p>音量值:<span id="audio-value">null</span></p>
</div>

<footer class="footer">
    <hr><p><span class="font-c-light">BY</span> Huooo <span class="font-c-light">AT</span> 2018-08-16 10:30:00</p>
</footer>
              
            
!

CSS

              
                .container{width:80%;min-height: 400px;margin:0 auto;overflow: hidden;}
.font-c-light{color:#aaa;}
.header, .footer{width:100%;text-align:center;}
a{text-decoration:none;color:rgba(230,0,0,1)}
              
            
!

JS

              
                var audioContext;
var mediaStreamSource = null
var meter = null

function beginDetect() {
  audioContext = new (window.AudioContext || window.webkitAudioContext)()
  if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
    navigator.mediaDevices.getUserMedia({audio: true}).then((stream) => {
      mediaStreamSource = audioContext.createMediaStreamSource(stream)
      meter = createAudioMeter(audioContext)
      mediaStreamSource.connect(meter)
    })
  }
}

function createAudioMeter(audioContext, clipLevel, averaging, clipLag) {
  const processor = audioContext.createScriptProcessor(512)
  processor.onaudioprocess = volumeAudioProcess
  processor.clipping = false
  processor.lastClip = 0
  processor.volume = 0
  processor.clipLevel = clipLevel || 0.98
  processor.averaging = averaging || 0.95
  processor.clipLag = clipLag || 750

  // this will have no effect, since we don't copy the input to the output,
  // but works around a current Chrome bug.
  processor.connect(audioContext.destination)

  processor.checkClipping = function () {
    if (!this.clipping) {
      return false
    }
    if ((this.lastClip + this.clipLag) < window.performance.now()) {
      this.clipping = false
    }
    return this.clipping
  }

  processor.shutdown = function () {
    this.disconnect()
    this.onaudioprocess = null
  }

  return processor
}

function volumeAudioProcess(event) {
  const buf = event.inputBuffer.getChannelData(0)
  const bufLength = buf.length
  let sum = 0
  let x

  // Do a root-mean-square on the samples: sum up the squares...
  for (var i = 0; i < bufLength; i++) {
    x = buf[i]
    if (Math.abs(x) >= this.clipLevel) {
        this.clipping = true
        this.lastClip = window.performance.now()
    }
    sum += x * x
  }

  // ... then take the square root of the sum.
  const rms = Math.sqrt(sum / bufLength)

  // Now smooth this out with the averaging factor applied
  // to the previous sample - take the max here because we
  // want "fast attack, slow release."
  this.volume = Math.max(rms, this.volume * this.averaging)
  document.getElementById('audio-value').innerHTML = this.volume
}
              
            
!
999px

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