To improve the acoustic performance of an existing masonry wall a number of steps can be taken. 

Initially, a check of the masonry wall can be carried out to identify any gaps which can result in an easy noise transfer route. Such gaps should be filled with suitable material.

Blockwork inner leaf can take a parge coat to seal over the whole surface of a blockwork wall prior to an internal lining system.

Siniat have a range of internal lining systems, better acoustic performance can be achieved with larger cavity size (which can be filled with insulation) and higher density plasterboards and number of layers. 

You will need to weigh up the cost and space an independent lining system compared to a direct bond lining or dryliner system which will use less space.

For performances and technical build-up see the Lining section of the Drywall Manual.