有趣的阅读题,我不知道tututututu是什么意思

有趣的阅读题,我不知道tututututu是什么意思
This story happened in a small town near London.In this small town there lived an old woman.Her son worked in London.One day,the old woman wanted to go to London to see her son.She got up early and reached the small station at nine o’clock in the morning.Because this was her first trip(旅行)to London,she did not know the train time.She was very worried.Just at that moment,she saw a litt
boy running towards her.She stopped him and asked him what time the train would arrive and when the train would leave for London.
The little boy looked at the woman,and said[tu:tu:tu:tu:tu:tu].Then he ran away.
The old woman was very surprised and got very angry.She thought and thought.At last,she began to smile,shouting,“ What a clever boy!He had told me the train time in such a way.