Shared Wall I can hear my neighbours talking

[aveatry]

One of my Airbnbs is a 19c Fishermans terrace and you can hear the neighbours plug something in the socket in the main bedroom.

The mind boggles

 

[Wayners]

Timber screwed to bricks
Acoustic insulation
Resilient bar



Now double plasterboard screwing boards to bars.
It's not cheap although easy enough.
Take some doing for the complete adjoining wall and about 130mm thick. That's 5 inches

 

[StephenStephen]

Could the sound be travelling through the void under the floor?