问题 单项选择题 B型题

声波频率>20kHz()。

A.次声波

B.可听声波

C.超声波

D.空间脉冲长度

E.脉冲宽度

答案

参考答案:C

解析:1.声波频率<16kHz时低于人耳听觉阈值的下限,称为次声波。2.声波频率>20kHz时超出了人耳听觉阈值的上限,称为超声波。3.声波频率在16~20kHz时能被人耳听到,称为可听声波。4.超声波的空间脉冲长度决定着最大轴向(深度)分辨力和深度定位的精确性。若在超声波轴向上有两个距离小于空间脉冲长度的反射体,这两处反射体合为一体,在图像上呈现为一个反射体。5.周期与某个脉冲中的循环周期数之积为脉冲宽度。超声仪纵向分辨力取决于超声脉冲的宽窄,脉冲越窄,纵向分辨力越好。

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                                Jazz concert
Are you interested in Jazz? There is a Jazz concert at 8:oopm on Sunday at Grand Hall
Tickets:
Adults(成年人 ) :  90 yuan
Children :   40 yuan
 
                                Lecture (演讲 )
Mr White will give a lecture about country music
Come and enjoy it at 6:30 on Saturday evening at Hongyang Theatre.
Tickets :  Free ( 免费的)
 
                                Beijing Opera
Do you like Beijing Opera? Come and enjoy yourself at 7:30 on Saturday evening at Changfeng Theatre.
Tickets:
Adults:  50 yuan
Children: 25 yuan
                                   Beethoven
Do you want to know more about Beethoven? There is a film about Beethoven at 2:30 at People’s Cinema on Saturday afternoon.
Tickets:
Adults:  30 yuan
Children: 15 yuan
小题1: Ben likes country music. He can go to______________.
A.People’s CinemaB.Hongyang Theatre
C.Changfeng Theatre D.Grand Hall
小题2:. Jack and his brother are both Jazz lovers. They can go to a Jazz concert on__________.
A.Saturday afternoonB.Sunday afternoon
C.Sunday eveningD.Saturday evening
小题3:. Jim loves Beijing Opera very much. He can see it at_____________.
A.2:30 pm B.7:30 pmC.6:00 pmD.6:30 pm
小题4:. Which of the following is TRUE?
A.You can listen to Mr White’s lecture without paying.
B.If Mr Black goes to Grand Hall with his ten-year-old son, he should pay 90 yuan
C.Uncle Li can see Beijing Opera on Saturday afternoon.
D.The film about Beethoven is at People’s Cinema on Saturday evening.
单项选择题