Verbal tick

Hi everyone, My seven year old has just started to do verbal ticks. He’s been doing it for about 3 months. He makes a grunting noise all the time. It sometimes gets so bad that when I listen to him read he wouldn’t breath because he has to make the noise. I have been wracking my brain about what and why it has started. We moved him and his sister schools and that was six months ago but nothing else has changed. He is incredibly happy at school, he’s always smiling, he always wants to go to school now, since he’s been at his new school he’s a different child the difference in my son is incredible he’s so happy and confident. The more content he seems the more sensory things are popping up.  I’ve spoken to school and they don’t hear it and I’ve spoken to the senco but I think she thinks if it’s not happening at school she’s not overly worried. I’ve mentioned it to him but he doesn’t even notice it. It doesn’t overly worry me (apart from the not breathing bit) but it’s the first time I’ve dealt with this. I don’t want to miss something. Any advice would be much appreciated.