Can you hear the "beating" of a fifth not being quite in tune?
Or the same with an octave, when you play a D-D open string and 3rd finger on A double stop - move the finger up and down a bit, and hear when it's exactly precise.
Then you can learn to hear pretty much the same thing, but without the double stop - when the open D responds to another D played precisely in tune.
Then the same with other open string notes in various places.
Then similar characteristics of other notes.
Different violins have these to a different extent (and it is a big part of an instrument being good), but it's still in large part learning to hear what's there.
Also, the first (?) chapter of Simon Fischer's Violin Lesson has a lot of good things about tone.
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