Sound sensory problem

Hi everyone one. I’m at lost and not sure what to do 😞 My son is 6 and coming 7 by end of this year. When school reopens, he went to school happily for the past 1 week and all the sudden he refused to get down from the car this morning because he said he’s scared of the whistle sound from the school security guard that is guiding the traffic at that time. He covered his ears tightly and no matter how i explained to him, he just couldn’t accept it and says he doesn’t want to go to school anymore 😭 My son actually have sound sensory sensitivity since young and not only whistle sound but there are other noises/sound too that he is scared of. So if it’s you, what will you do?