Breathing in Character Select Menu

Hello! The other day I started noticing a strange and very quiet sound that was playing after selecting Pico or Boyfriend in the Character Select Menu. This sound only plays after restarting the game and is different each time. If you look at the FPS, it plays as you might expect right before the Freeplay Menu loads. This sound often resembles breathing. What is this? Is it a bug or are the developers up to something?