There are several possibilities
1/ main water stopcock has loose washer which is vibrating
2/ ball valve on toilet or hot water tank
3/ faulty tap allowing air into system
When noise is present check at stopcock to see if loudest there then check toilet and water tank for noise.
Finally try turning on each tap in turn when noise is present.
Also turn off water at stopcock then turn back on wind stop valve all the way on then a quarter turn clockwise.