第十课 Lesson Ten 1.各种各样的声音。 All kinds of sounds. 2.用录音机录下生活中的各种声音。 Recording various sounds in life with a recorder. 3.准备小鼓、锣 、橡皮筋、水杯、锯条。 Prepare drum, Gong, rubber band, water cup and saw blade. 4.声音大小和音调的高低。 The size and pitch of the sound. 5.用力的不同声音的大小也不同。 The intensity of the sound varies with the force. 6.声调有时高有时低。 The tone is sometimes high and sometimes low. 7.听不见的声音。 An inaudible sound. 8.蝙蝠能利用超声波探测障碍物 Bats can use ultrasound to detect obstacles 9.医院用B超探测病灶 Detection of lesions by B-ultrasound in hospital 10.潜水艇利用声纳导航 Submarine navigates with sonar 11.人耳能听到的声音。 Sound that can be heard by the human ear. 12.次声波20赫兹超声波20000赫兹。 Infrasonic wave 20 Hz ultrasonic wave 20000 Hz. 13.资料卡。 index card for files. 14.次声波和超声波。 Infrasonic and ultrasonic waves. 15.人耳能听到的声波频率为20～20000赫兹。 The frequency of sound wave can be heard by human ear is 20-20000 Hz. 16.因此，当物体的振动产生的声波超过一定频率，即高于人耳听觉上限时，人们边听不到了，这样的声波称为超声波。 Therefore,when the sound wave generated by the vibration of an object exceeds a certain frequency. that is. higher than the upper limit of human ear hearing. people can not hear is.such sound wave is called ultrasonic. 17.次声波是振动频率低于20赫兹的一种低频率波。 Infrasonic wave is a kind of low frequency wave whose vibration frequency is lower than 20 Hz. 18.由于次声波的振动频率低于人耳的正常接收范围，所以大部分人听不到它。 Because the vibration frequency of infrasound wave is lower than the normal receiving range of human ear.most people can't hear it. 19.次声波不依靠其他辅助设备，能在地球上传播很远的距离。 Infrasound can travel a long distance on the earth without other auxiliary equipment. 20.它由于在传播的过程中性质较稳定，能量衰减幅度小，穿透力强，因此可用于定向导航。 It can be used in directional navigation because of its stable property.small energy attenuation and strong penetration. 21.次声波自被发现以来，已经广泛应用于军事领域。 Infrasonic wave has been widely used in military field since it was discovered. 22.调查、了解超声波和次声波在生活中的应用。 Investigate and understand the application of ultrasound and infrasound in life. |
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