I followed the W3C's Documentation to implement a "vumeter" (code) using JavaScript's Web Audio API specifically the AudioWorkletProcessor and AudioWorkletNode interfaces. I would like to know why is the RMS level is compared with the previous volume multiplied by a "smoothing factor" (sorry I just started learning this topic so it's all new for me):

 // Calculate the RMS level and update the volume.
 rms = Math.sqrt(sum / samples.length);
 this._volume = Math.max(rms, this._volume * SMOOTHING_FACTOR);

Also what is the range that the volume's variable can take? Is it possible to know so that we can assume that the volume will be a value in a 0...100 range?

Process method code:

process (inputs, outputs, parameters) {
    const input = inputs[0];
    // Note that the input will be down-mixed to mono; however, if no inputs are
    // connected then zero channels will be passed in.
    if (input.length > 0) {
      const samples = input[0];
      let sum = 0;
      let rms = 0;
      // Calculated the squared-sum.
      for (let i = 0; i < samples.length; ++i)
        sum += samples[i] * samples[i];
      // Calculate the RMS level and update the volume.
      rms = Math.sqrt(sum / samples.length);
      this._volume = Math.max(rms, this._volume * SMOOTHING_FACTOR);
      // Update and sync the volume property with the main thread.
      this._nextUpdateFrame -= samples.length;
      if (this._nextUpdateFrame < 0) {
        this._nextUpdateFrame += this.intervalInFrames;
        this.port.postMessage({volume: this._volume});
      }
    }
    // Keep on processing if the volume is above a threshold, so that
    // disconnecting inputs does not immediately cause the meter to stop
    // computing its smoothed value.
    return this._volume >= MINIMUM_VALUE;
  }