用JavaScript写用麦克风采集音频并将音频转换格式为16k16bits单声道音频，再转为blob传输给后端的代码

以下是使用JavaScript采集音频并将音频转换格式为16k16bits单声道音频并将其转换为blob的示例代码：

const audioContext = new (window.AudioContext || window.webkitAudioContext)();
const bufferSize = 2048;
const recordingTime = 5000;
let audioData = [];

navigator.mediaDevices.getUserMedia({ audio: true })
  .then(stream => {
    const mediaRecorder = new MediaRecorder(stream);
    mediaRecorder.start();
    const audioChunks = [];
    mediaRecorder.addEventListener("dataavailable", event => {
      audioChunks.push(event.data);
    });

    setTimeout(() => {
      mediaRecorder.stop();
      stream.getTracks().forEach(track => track.stop());
      const audioBlob = new Blob(audioChunks);
      const reader = new FileReader();
      reader.readAsArrayBuffer(audioBlob);
      reader.onloadend = () => {
        audioContext.decodeAudioData(reader.result, (buffer) => {
          const audioBuffer = convertBuffer(buffer);
          const audioBlob = bufferToBlob(audioBuffer);
          sendBlobToServer(audioBlob);
        });
      };
    }, recordingTime);
  });

function convertBuffer(buffer) {
  const sampleRate = buffer.sampleRate;
  const numberOfChannels = buffer.numberOfChannels;
  const length = buffer.length;
  const newBuffer = audioContext.createBuffer(1, length, sampleRate);
  const newChannel = newBuffer.getChannelData(0);

  for (let i = 0; i < length; i++) {
    let channelSum = 0;
    for (let j = 0; j < numberOfChannels; j++) {
      channelSum += buffer.getChannelData(j)[i];
    }
    newChannel[i] = channelSum / numberOfChannels;
  }

  return newBuffer;
}

function bufferToBlob(buffer) {
  const numberOfChannels = buffer.numberOfChannels;
  const length = buffer.length;
  const newBuffer = new ArrayBuffer(length * numberOfChannels * 2);
  const newView = new DataView(newBuffer);

  for (let i = 0; i < length; i++) {
    let offset = i * numberOfChannels * 2;
    for (let j = 0; j < numberOfChannels; j++) {
      let sample = Math.max(-1, Math.min(1, buffer.getChannelData(j)[i]));
      sample = (sample + 1) / 2 * 65535;
      newView.setInt16(offset, sample, true);
      offset += 2;
    }
  }

  return new Blob([newView], { type: "audio/wav" });
}

function sendBlobToServer(blob) {
  const xhr = new XMLHttpRequest();
  xhr.open("POST", "/api/upload-audio", true);
  xhr.setRequestHeader("Content-Type", "audio/wav");
  xhr.send(blob);
}

此代码通过调用Web API中的`getUserMedia`方法来获取音频流，使用`MediaRecorder`对象来记录音频数据，然后将记录的音频数据转换为blob，并使用`FileReader`对象将其读入内存中。然后，使用`decodeAudioData`方法将Blob数据解码为音频缓冲区，然后使用`convertBuffer`函数将音频缓冲区转换为单声道的16k16bits音频缓冲区，最后将缓冲区转换为Blob并发送到后端。

请注意，此示例代码仅用于参考。实际应用中可能需要根据具体需求进行修改。