Correct use of the word "legible"
In summary, "legible" is not the idiomatically correct term to use to indicate that audible voice sounds are intelligible. If you use the term it might be understood as you desire, but could cause confusion.
You can, as described above, use "audible","intelligible", "discernible", "hearable", "recognizable", "readable", "loud and clear", and a few others to indicate successful reception of the audio.
But note that one would not normally say "You are coming in audible", but rather "You are audible." "Coming in" would be reserved for "You are coming in loud and clear", and a few other idiomatic terms.
M-W licenses the broadening of the application of 'legible' to include other 'readable language':
Full Definition of legible
1 : capable of being read or deciphered : plain
2 : capable of being discovered or understood
...
an anxious mood that was clearly legible upon her face
As does AHDEL,
- Plainly discernible; apparent: a legible weakness in disposition.
Collins, and RHK Webster's:
- capable of being discerned or distinguished: Anger was legible in his behavior.
However, applying this metaphorical broadening to the clarity of sound (reception) would be non-standard and unwise.