Tics

Hi. I have an 8 year old grandson with autism. We are used to his various tics which come and go but his latest one is driving us to distraction. We ignored it as we always do but this one is constant and so irritating. We understand his need to tic but distracting etc doesn't work. My daughter, his mum, has asked him to stop (which goes against the grain) and he gets angry and upset but does stop for a while but it soon returns. I worry that by asking him to stop doing something that he feels the need to do might cause him psychological harm or am I thinking too deeply? The noiseas are so difficult to live with.