问题
单项选择题
中频噪声与高频噪声的分界线是( )。
A．100Hz
B．500Hz
C．1000Hz
D．5000Hz
答案
参考答案：C
解析： 噪声按其频率成分的分布，可分为：低频噪声(500Hz以下的噪声)、中频噪声(500～1000Hz)和高频噪声(1000Hz以上的噪声)。
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中频噪声与高频噪声的分界线是( )。
A．100Hz
B．500Hz
C．1000Hz
D．5000Hz
参考答案：C
解析： 噪声按其频率成分的分布，可分为：低频噪声(500Hz以下的噪声)、中频噪声(500～1000Hz)和高频噪声(1000Hz以上的噪声)。
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| It was very cold outside my car. I did not want to get out of it 1 we passed by a cafe. Suddenly I noticed a short old man, covered with some bits of cloth, shaking with the cold. He was waiting for anyone who would 2 him a coin or a cup of hot coffee. I asked my 3 to go over and hand this old man something. He looked into my husband's face, smiled and said, " 4 ". I felt so happy and I wished the old man could live 5 the cold night. I was sure to meet him again and find out how he was the next 6 , as I have to pass this way every day, I did so the next evening, and he remembered the 7 and came up to my window and smiled at me. This time I offered him a 8 of food. He reached out for the bag and I gave him my hand. He 9 the food, smiled and said, "May God bless you." I looked at the old man and he 10 me think of my father. I do hope all of us will remember that maybe one day, it could happen to one of us, 11 please do not pass by a 12 person without offering at least a word of love and a kind smile or an act of kindness of any kind. | ||||
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