The service valve that is on the supply pipe is half closed, it will create turbulence set like that and turbulence means noise.
It's typical when trying to reduce mains flow to outlets where the mains flow is too high for it when going from gravity to mains. If you open the valve fully, slot in line with the pipe and the noise decreases, then there's your issue. You may then need a new fill valve if it has been running on gravity fed cold water until now.
Agree with others that this should have been considered by the plumbers doing the work. As part of the conversion it is always required to consider the outlets when changing from gravity to mains pressure.
It's typical when trying to reduce mains flow to outlets where the mains flow is too high for it when going from gravity to mains. If you open the valve fully, slot in line with the pipe and the noise decreases, then there's your issue. You may then need a new fill valve if it has been running on gravity fed cold water until now.
Agree with others that this should have been considered by the plumbers doing the work. As part of the conversion it is always required to consider the outlets when changing from gravity to mains pressure.