They really are AWFUL. Yes, the insulation in the flat is very poor, but I just don't think it's considerate to blast jazz music each and every night, where the bass shakes the floor. Occasionally, this goes on past 11pm. Our bedroom is above their lounge where the damn speakers are. Our baby sleeps above all this noise. And they know we have a baby.
I know life doesn't and shouldn't stop for others if someone else has a baby, but is it unreasonable for me to think they could have the music a little quieter?