code: @Override
      public Sample addNoise(List<Sample> samples) {
          Sample appended = Mixer.append(samples);
          String noiseFile = _noiseFiles[RAND.nextInt(_noiseFiles.length)];
          Sample noise = SampleUtil.readSample(noiseFile);
  
          // Decrease the volume of the noise to make sure the voices can be heard
          return Mixer.mix(appended, 1.0, noise, 0.6);
      }
docs: {@inheritDoc}
  
  Append the given <code>samples</code> to each other, then add random
  noise to the result.