My friend played the mosquito noise behind the teacher and there was no response.
I saw somebody using their cell phone and playing the mosquito noise in class. All of the kids were annoyed and looking at him, but the teacher couldn't hear it. In the shop room, we always think someone is playing the noise, but it is just this old computer. We had this substitute once, and she was REALLY wierd. When somebody said the word "sucks", she said, "No, it doesn't suck. Words like that don't make a positive environment. Say it vaccuums."