Here is a list of ear training apps that I would recommend: Complete Ear Trainer - Gamified learning experience taking you through the basics of interval recognition, chord spelling, scale recognition and more! Functional Ear Trainer - Specializes in scale degrees and melodic dictation.

Here I go through and identify 2nds and 5ths by ear.

Ear training, also known as aural skills is the process of developing one's ability to recognize and interpret musical elements solely by listening. It involves honing skills such as pitch recognition, interval identification, chord quality identification, rhythmic comprehension, and melodic dictation. Ear training is essential for musicians of all levels and disciplines, as it enhances musical perception, improves performance accuracy, facilitates music transcription and memorization, and supports improvisation and composition. Through focused practice and exercises, ear training helps musicians develop a keen ear, allowing them to better understand, appreciate, and interact with music.