My fucking neighbors

I live in a 4-floor building, lost in a quiet neighborhood on the hill. I'm happily married to my husband of 3 years, we have a 1-year-old son called Harold. Of course, since we had Harold, our sex life has gone down quite a bit. We have a very happy marriage - he works, and I stay at home. But the carnal passion of my teenage/20s is gone - when we have sex, nowadays, it's to release tension rather than give in to stronger-than-life temptations.

Recently, my upstairs neighbor started seeing this girl. He's quite nice, I've talked with him a few times. The girl is sweet too, pretty, and a bit younger. But, oh my god. Often, in the morning, I take Harold out on the terrace, where we hear the birds sing and the noise of the city. But not only. My neighbor and the girl fucking, very, very loudly. I am worried for Harold- should he be exposed to these sounds, even though he has no idea what they are?

But, in my tired housewife dry spell, I listen to the sounds they emit, like little hints that inspire me into my own sexual dreams. From the loud banging on the walls, I imagine her, her face pressed against the rough texture of the plaster walls, and him binding her hands behind her as he penetrates her from behind. From her screams and his low-pitched moans, I imagine a symbiotic exchange of pleasure. She goes down on him. He goes down on her, tending to all of her sexual desires. Sometimes, I think they get creative– I hear foreign sounds, like the whip of a wooden spatula on bare skin, or a loud shower that is lasting suspiciously long...

And all this while feeding Harold his morning applesauce. It makes me quite guilty– for he listens too, without knowing anything.