https://www.musical-u.com/learn/why-do-unison-and-octave-intervals-sound-the-same/
Why do unison and octave intervals sound the same?
Harmonic unison and octave intervals are difficult to distinguish. It can be frustrating when taking a quiz, but it does reflect a real musical challenge.
Find out why in the article below:
https://www.musical-u.com/learn/why-do-unison-and-octave-intervals-sound-the-same/