Hi @Ed_Waadt !
An acoustic engineer could certainly answer much much much better than me but consider that sound travels through air and through different mediums, activating particules differently: airborne sounds and impact sounds. Between high and low pitched sounds, probably you hear much more the low frequency sounds of your neighbours’ TV because they penetrate better the wall or the floor between appartements. As a way to improve acoustic insulation you would need to add more layers (including non rigid insulation and service cavity). The composition with materials of different masses/densities would absorb a broader spectre of sounds and provide more peaceful evenings I’m maybe simplifying things a bit too much for the sake of clarity, but any acoustic engineer can do the maths and dimension all these layers.
Impact sounds are also a common issue - related to vibrations that are transferred through materials (i.e. kids that “gently” run and jump around all day long - like kids are supposed to do). These situations are can be solved during the construction phase with good details (i.e. isolate structural elements, use acoustic sealants, non-rigid connections, in order to break the pathway that allows the transmission of impact noises).
I’m not sure you’re entitle to a rent reduction… I guess you wouldn’t be an isolated case.
Have you tried to talk with your neighbour? Sometimes one doesn’t realise how much noise passes through the walls… TV flat screens usually have the speakers agains’t the wall at the back which wouldn’t help in your case.
Yes, ongoing projects and work mainly in Suisse Romande at the moment.