js实现声学测试

实现声学测试的JavaScript方法

使用Web Audio API进行频率分析

Web Audio API提供了分析音频信号的能力，可以通过AnalyserNode获取频率数据。以下代码展示如何创建音频上下文并分析频率：

const audioContext = new (window.AudioContext || window.webkitAudioContext)();
const analyser = audioContext.createAnalyser();
analyser.fftSize = 2048;

// 连接麦克风输入
navigator.mediaDevices.getUserMedia({ audio: true })
  .then(stream => {
    const source = audioContext.createMediaStreamSource(stream);
    source.connect(analyser);

    const bufferLength = analyser.frequencyBinCount;
    const dataArray = new Uint8Array(bufferLength);

    function analyze() {
      analyser.getByteFrequencyData(dataArray);
      // 处理频率数据
      requestAnimationFrame(analyze);
    }
    analyze();
  });

生成测试音调

可以使用OscillatorNode生成特定频率的测试音调：

function playTestTone(frequency, duration) {
  const oscillator = audioContext.createOscillator();
  const gainNode = audioContext.createGain();

  oscillator.type = 'sine';
  oscillator.frequency.value = frequency;
  oscillator.connect(gainNode);
  gainNode.connect(audioContext.destination);

  oscillator.start();
  gainNode.gain.setValueAtTime(1, audioContext.currentTime);
  gainNode.gain.setValueAtTime(0, audioContext.currentTime + duration);
  oscillator.stop(audioContext.currentTime + duration);
}

测量音频延迟

通过记录发送和接收时间差来测量系统延迟：

let startTime;
function measureLatency() {
  startTime = audioContext.currentTime;
  playTestTone(1000, 0.1);

  const scriptProcessor = audioContext.createScriptProcessor(2048, 1, 1);
  scriptProcessor.onaudioprocess = function(e) {
    const input = e.inputBuffer.getChannelData(0);
    // 检测测试音调
    if (detectTone(input)) {
      const latency = audioContext.currentTime - startTime;
      console.log(`系统延迟: ${latency.toFixed(2)}秒`);
    }
  };
  analyser.connect(scriptProcessor);
}

实现频率响应测试

通过扫描频率范围并测量输出强度来测试频率响应：

function frequencySweep(startFreq, endFreq, duration) {
  const oscillator = audioContext.createOscillator();
  const gainNode = audioContext.createGain();

  oscillator.type = 'sine';
  oscillator.frequency.setValueAtTime(startFreq, audioContext.currentTime);
  oscillator.frequency.linearRampToValueAtTime(
    endFreq, audioContext.currentTime + duration
  );

  oscillator.connect(gainNode);
  gainNode.connect(audioContext.destination);
  gainNode.gain.value = 0.5;

  oscillator.start();
  oscillator.stop(audioContext.currentTime + duration);
}

可视化音频数据

使用Canvas绘制频率或波形图：

function drawWaveform(canvas, dataArray) {
  const ctx = canvas.getContext('2d');
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  ctx.lineWidth = 2;
  ctx.strokeStyle = 'rgb(0, 255, 0)';
  ctx.beginPath();

  const sliceWidth = canvas.width / dataArray.length;
  let x = 0;

  for(let i = 0; i < dataArray.length; i++) {
    const v = dataArray[i] / 128.0;
    const y = v * canvas.height/2;

    if(i === 0) {
      ctx.moveTo(x, y);
    } else {
      ctx.lineTo(x, y);
    }
    x += sliceWidth;
  }
  ctx.stroke();
}

这些方法组合使用可以实现完整的声学测试功能，包括频率分析、延迟测量、频率响应测试和结果可视化。实际应用中需要根据具体测试需求调整参数和算法。