Shower mixer boisterous? just installed a mixer in shower and tub, the bath tub mixer...

just installed a mixer in shower and tub, the bath tub mixer is silent whereas the shower mixer is very piercing, it sounds like high pressure. Any one have a similar problem?
Drill hit holes within an acrylic tub?
Answers:    try taking out the cartridge and cleaning the valve. I don`t know even replace the cartridge
Would a regular drill near a tiny bit...
YES I GET THE SAME PROBLEM, ITS A HIGH PITCH NOISE AND AS YOU SAID ITS COULD BE DOWN TO THE PRESSURE GOING THROUGH THE SMALL PIPE THAT LEADS TO THE SHOWER HEAD. WHAT YOU COULD TRY IS TURN THE PRESSURE DOWN ON BOTH FEEDS AND SEE IF THAT SORTS IT