https://www.musical-u.com/learn/the-space-between-hearing-and-singing-intervals/
At Musical U, you’ll learned some of the basic principals of solfege syllables and how to determine the tonic. Now let’s discuss intervals.
Recognizing the distinct sound of different intervals and being able to sing them back accurately in solfege will go a long way with developing transcribing skills. https://www.musical-u.com/learn/the-space-between-hearing-and-singing-intervals/