Is there a formula or chart that specifies what lowpass filter LAME will automatically invoke for certain bitrates? I've looked around the net and can't find anything on this.
And is there a specific logic that dictates said formula or chart, besides just listening tests?
Source: http://wiki.hydrogenaud.io/index.php?title=LAME#Recommended_settings_details
Deeper source(code): https://github.com/rbrito/lame/blob/origin/libmp3lame/lame.c#L211
Update:
--preset insane seems to be using a lowpass filter as well...
see LAME: Why is a lowpass filter used with --preset insane
--preset insane seems to be using a lowpass filter as well... see sound.stackexchange.com/questions/38109/…