soundproofing my semi?

[movingonup2015]

Hi, just looking for some advice on soundproofing my 1930's semi.

For some reason in my house I can hear my neighbours, clear as day, its like they are in my house I have lived in a 1930's semi before this one and it wasn't anywhere near as bad. It has cavity wall insulation and loft insulation if that helps.

I don't want to go down the route whereby I'm putting up new false walls everywhere with the acoustic plasterboard stuff so I'm wondering there must be some way that it's leaking through as this is definitely not normal. Its not like they are excessively noisy (although when they are its a lot worse obviously!) I can hear their discussions when they are talking normally - clear as day!

they smoke weed also and when I come into my house it absolutely stinks - if you were visiting you would swear it was me that was smoking it, its that strong!

so obviously theres holes somewhere I just don't know where to begin looking really. All the windows are sealed properly that was the first thing I checked.

I don't have carpet in my main bedroom at the moment as I am coming to the end of renovating, also my dining room doesn't have flooring down I could lift the floorboards up if needed, so is there anything I can put on the wall underneath the floor between my property and theirs to reduce the smells and noise?

Do both houses still have the chimney breasts in place? Is their downstairs open plan? About the weed smoking - I found in the house we used to live in when the next door neighbours smoked cigarettes indoors (every evening) it smelled like weed in one of our adjoining rooms. Definitely wasn't though.

In a previous house of ours the sound carried through the floorboards between the ground and first floor.

Yes both still have the chimney breasts and theirs isn't open plan their living room backs onto mine, dining room backs onto mine etc.
Its definitely weed - not only have they bragged to me about how they like to relax with it but as I can hear them clear as day I hear them talking about how much they are going to buy that day/week off their landlord.

also their little girl tells me on a regular basis that daddy smokes weed and she doesn't like it because it makes her cough.... lovely!

any suggestions about what I could seal the wall with? will I get any problems if I seal it?

I was told by someone with a physics degree that sound in adjoining houses travels/vibrates along the joists supporting the floor above. Therefore insulating walls etc will do only so much, not cut the noise of neighbours out completely. There will still be a problem and esp if you have chimney breasts backing onto each other.

After years of noise from neighbours in different properties, I have opted for bungalows, much more peaceful and also easier to insulate via the party wall.

Do not know anything about cutting out smells from next door neighbours I'm afraid.