message: Example: SLM 2-chan, Improve comments
diff: * SoundLevelMeter_2Chan
  *
  * Created: Chip Audette, OpenAudio
  -* Original: SoundLevelMeter (1 channel), June 2018
  +* Original: SoundLevelMeter (which was 1 channel), June 2018
  * Updated: Expanded to two channel, running at 96 kHz, March 2019
  *
  * Purpose: Compute the current sound level, dBA-Fast or whatever
  