How to dynamically speed up word gaps in audio playback with javascript?

const formatDecibel = val => {
  val = 10 * Math.log(val) * Math.LOG10E;
  if (val === -Infinity)
    return "−∞";
  if (val < 0)
    return `−${(-val).toFixed(1)}`;
};

document.addEventListener('DOMContentLoaded', function () {
  const audio = document.getElementById('audio');
  // 2048 sample buffer, 1 channel in, 1 channel out
  const meter = document.getElementById('meter');
  const labelFast = document.getElementById('label-fast');
  const labelLoud = document.getElementById('label-loud');
  const chkSkip = document.getElementById('chk-skip');

  const handler = () => {
    const ctx = new AudioContext();
    const processor = ctx.createScriptProcessor(2048, 1, 1);

    processor.onaudioprocess = function (evt) {
      const input = evt.inputBuffer.getChannelData(0);

      const rms = Math.sqrt(
        input.map(val => val * val).reduce((a, b) => a + b, 0)
        / input.length
      );

      if (chkSkip.checked) {
        if (rms < 0.002) {
          audio.playbackRate = 4;
        } else if (rms >= 0.004) {
          audio.playbackRate = 1;
        }
      } else {
        audio.playbackRate = 1;
      }

      meter.value = rms;
      labelLoud.textContent =
        `${formatDecibel(rms)}\xa0dB FS (LPCM RMS ${rms.toFixed(5)})`;
      labelFast.textContent =
        `${audio.playbackRate}×`;
    };

    const source = ctx.createMediaElementSource(audio);
    source.connect(ctx.destination);
    source.connect(processor);
    processor.connect(ctx.destination);
  };

  audio.addEventListener('play', handler, { once: true });
}, { once: true });

<p> <audio crossorigin='anonymous' id='audio' controls
  src='https://upload.wikimedia.org/wikipedia/commons/0/08/Split_infinitive.ogg' style='width: 100%'></audio>
<p> <label><input id='chk-skip' type='checkbox' checked> Skip silence</label>
<p> Loudness: <meter id='meter' style='width: 15em;'></meter> <span id='label-loud' style="display: inline-block; width: 20em; text-align: right;">−∞ dB FS</span>
<p> Speed: <span id='label-fast'>1×</span>