Nice little game, especially considering it's your first one.
The main character is somewhat mismatched with the rest of the 3D props, but it's a pretty minor thing.
I liked the scene switching mechanics, but I have to say I really didn't enjoy the static noise transitions. It feels really jarring and fatiguing to me, both visually and audibly, especially since you have to switch between them very often to solve the puzzle. If you could change it to a smoother, much gentler transition, I think it will improve the player experience much better. It would also fits the rest of the game more.
I would also tweak the jumping a bit to make the player not as floaty. I would also add pitch-shifting to the footstep sounds to make it less monotonic.
Overall, still a decent entry. Keep up the good work!