Who is whistling ?!!

Once, there is a doctor in a university and he was explaining a lecture. Suddenly, he has heard a whistling voice. So, he asked his students : Who has toot right now !! Then, no one answered. So, the doctor continued his explanation. Then again, he has heard a whistling voice. Again, he asked his students the same question and no answer. So, the doctor stopped explaining and closed the book and said the lecture has done ! but I just want to tell you this story quickly before I leave. Then, he continued : Yesterday, I couldn’t  sleep so I think if I walked on the street I will feel better. So I have started on my car. Suddenly, I have seen a beautiful girl gesturing to me so I have asked her : Do you want me to transport you my dear ?! she answered : oh, I wish that … That’s all. After I transported her, I asked for her name, she kissed me and replied : I will not tell you my name, but my brother studied on your class and always he likes to whistle. Suddenly, all students have looked at the student who whistles. so, the doctor laughed and ordered the student to go out.