https://www.musical-u.com/learn/how-do-you-use-intervals-to-recognise-notes-by-ear/
When musicians ask themselves “why learn intervals?” often the answer is “to recognise notes by ear”.
Intervals can be seen as the “building blocks” with which melodies and harmonies are created, and so interval ear training helps you to pick apart these elements of music by ear and recognise the notes present. However, where many music students get stuck is that even when you learn to recognise intervals, it is not immediately obvious how to use that new skill to recognise notes in music you hear.
There are three ways you can apply the knowledge of intervals to recognise notes by ear:
https://www.musical-u.com/learn/how-do-you-use-intervals-to-recognise-notes-by-ear/