I have been wanting to comment about this for some time.
The quality of the audio is somewhat important but not a qualifier.
But what I at least WANT is the level of volume to be normalised at 95%.  Its hard to hear in a noisy environment like a car or places with background noise.
This is easy for a submitted sample.  Run all input/submits through a normaliser/compressor.
Volume checks in mumble/radio should also normalise.