How long does it take before you start noticing changes in your teeth due to lingual braces?

Depends: On your particular case. What i would do is ask the orthodontist every now and then (say once a month or so) to show you your pre braces model so you can see the change. When you are checking daily it is hard to tell if anything is happening, however i assure you it is and in the end you will be amazed.

FEW WEEKS: Lingual braces will usually start showing results within a few weeks to a few months.

Almost immediately: Whether braces are on the outside or on the inside of the teeth, movement should begin almost immediately. Know that it takes longer to treat with lingual braces as each step taken is a smaller step, but movement will occur.