I recently had a loft conversion and the rest of the house replumbed and a new worcester bosch boiler installed on the bottom floor. The middle floor shower has a mixer where you turn the handle round to activate the shower with a tap in the middle of it to regulate the temp. The same setup is in the shower in the loft ensuite. The difference is that in the loft ensuite, when you turn on the water, the pipes make a whirring sound. If i turn on the tap in the ensuite basin then the sound dissipates, i guess due to less pressure being in the pipes. Could the mixer be causing this or is it just becasue it is higher up than the middle floor shower that the water has to travel further thus more pressure? I took of the shower head and the sound is still there but not as bad.