| Sound moves from its source to the ear
by wave like fluctuations in air pressure, something like the peaks and troughs
or the lowest point of ocean waves. One way to keep from hearing sound is to use
ear plugs. Another way is to cancel out the sound with anti-sound. Using a noise maker controlled by a microprocessor, engineers have produced sound waves that are half a wavelength out of phase with those of the noise to be quieted--each peak is matched to a trough, and vice versa. Once the researchers have recorded the offending sound, a microproce A. composing music B. repairing alarm systems C. eliminating engine noises D. intensifying fog warning sounds [多选题]交流进线开关设置“ ”三种模式。
A.自投手复 B.手投手复 C.自投自复 D.手投自复 [单选题]旅客列车乘务员发现旅客吸烟应( )。
A.予以职责 B.予以制止 C.进行宣传 D. 进行劝阻 [判断题]车辆人力制动机通过杠杆，可将拉力扩大数倍，从而产生制动力。（ ）
A.正确 B.错误 [判断题]隧道中可以采用有纤维绕包外层的电缆。
A.正确 B.错误 [单选题]矿山救护队每月至少进行1次佩戴氧气呼吸器的训练,每次佩戴氧气呼吸器的时间不少于[ ];每季至少进行1次高温浓烟演习训练。( )
A.2h B.3h C.3.5h D.4h [单选题]空压机空气过滤器主要由( )滤芯与壳体组成。
A.制动 B.运动 C.静止 [简答题]一般情况下，新钻头比旧钻头钻速快，在录井过程中中，可根据钻头类型、新度等情况识别所钻地层岩性。
[判断题]超重超限货物装车前货运员（外勤）确认待使用的车种、车型、车数符合批示电报和装车要求，加固材料和加固装置的规格、数量及质量符合装载加固方案规定。
A.正确 B.错误 我来回答: 提交
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