why is my mira advance shower humming?

I had a plummer repair a tap washer in the kitchen, he turned of the cold water to the house, when the cold water was turned back on, my son who was in the bathroom said some water came out of the shower head, even though it was not on. the next morning i could hear it humming from the bedroom when my husband was taking a shower, if you place your hand on the shower box you can feel it vibrating,if you put a little pressure on the front of the shower box it gets louder, before this started it randomly got hot and cold