high pitch whistling noise in the incoming water supply

[gero]

our incoming water mains pipe is lead from the utility supply stop cock for about 2mtr's it's joined to mdpe blue plastic pipe which run's into the house and join's a short piece of copper to our stop cock,both joints are grippa connections.our problem is that at night about midnight or later we get a high whistling noise from this water pipe and it goes at about 6/7am,there is no loss of water pressure, no spluttering of water in the tap off the mains or dirt in the water!even when we turn off the stop cock in the house the whistling is stilll loud in the supply pipe and is carried through to the rising waterpipe to the attic water tank.we dont have a water meter or prv on the utility supply stop cock out on the foothpath,any suggestions welcome welcome as we are losing sleep big time

 

[andytheplumber]

Sounds to me like the workman dropped a whistle in the pip es

 

[Mushybees]

Water pressure is higher at night.
Knock the water off at the external stop cock and either replace the internal one or crack it open and check the washer and valve seating.

 

[gero]

Water pressure is higher at night.
Knock the water off at the external stop cock and either replace the internal one or crack it open and check the washer and valve seating.

thks for ur reply,i have replaced the internal stop cock all going well so far with no whistling.i dont understand where the noise was coming from as it was suggested that the water pressure was reduced at night by the water comp cutting down on pumping,i have no leaking taps,attic tank ball cock or cisterns so there was no flow in the main pipe to produce the whistling noise,could the grippa connection of the blue mdpe to the half inch copper pipe in the house at the stop cock produce this noise?