freq(freq, time) {
    var t = time || 0;
    if (freq <= 0) {
      freq = 1;
    }
    if (typeof freq === 'number') {
      this.biquad.frequency.cancelScheduledValues(
        this.ac.currentTime + 0.01 + t
      );
      this.biquad.frequency.exponentialRampToValueAtTime(
        freq,
        this.ac.currentTime + 0.02 + t
      );
    } else if (freq) {
      freq.connect(this.biquad.frequency);
    }
    return this.biquad.frequency.value;
  }
Set the filter frequency, in Hz, from 10 to 22050 (the range of
 human hearing, although in reality most people hear in a narrower
 range).

 @method  freq
 @param  {Number} freq Filter Frequency
 @param {Number} [timeFromNow] schedule this event to happen
                               seconds from now
 @return {Number} value  Returns the current frequency value