Enhancement: Don't complain about background noise

[jmkristian]

The output from Direwolf often complains "Audio input level is too high" for short packets but not for long packets. It stops complaining if I activate squelch in the radio. But that's bad, as David explained.

I guess audio samples immediately preceding or following a received packet are included in the calculation of loudness. Since an open squelch with no signal is much louder than a good signal, and the good signal is relatively brief, the result is too high. A longer packet provides a larger sample of low audio, which yields a more accurate calculation. I guess.

It would be pleasant to eliminate these insignificant complaints. They're distracting, especially because they're colored red in the log.