Hey there :)

*edit: I think I made out the problem block, since in my roof there are some parts that are only 1 layer Spruce_slabs. And if I go into the forest and build myself into spruce_slabs the sounds remain.

I'm playing in 1.21.7.
My house is in a old spruce taiga and I hear the birds and stuff as loud as outside of the house.
I can't find any holes in my walls/roof and if I walk into the very corner of the room (2 sides cobblestone besides me) the sounds become quiet. But everywhere else in the house I hear the sounds.

My walls are made of Spruce_log,Spruce_slab,Spruce_wood,Cobblestone,Cobblestone_slab,spruce_doors,glass,(dirt in one room)