超声波的频率大于___Hz，次声波的频率小于___Hz．

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2022-06-09 问题

超声波的频率大于_Hz，次声波的频率小于_Hz．

2022-06-07 问题

An open pipe of air supports standing waves at frequencies of 300 Hz and 400 Hz. There are no other frequencies between these two. What is the frequency of the second harmonic of this tube? A: 100 Hz B: 200 Hz C: 400 Hz D: 600 Hz

An open pipe of air supports standing waves at frequencies of 300 Hz and 400 Hz. There are no other frequencies between these two. What is the frequency of the second harmonic of this tube? A: 100 Hz B: 200 Hz C: 400 Hz D: 600 Hz

2022-05-31 问题

‍一机车汽笛频率为750 Hz,机车以时速90公里远离静止的观察者.观察者听到的声音的频率是(设空气中声速为340 m/s). A: 810 Hz. B: 699 Hz. C: 805 Hz. D: 593 Hz.

2022-06-07 问题

Calculate the low frequency break point due to the capacitor CS for this BJT amplifier. [img=401x275]1803966add25148.png[/img] A: fLs = [img=98x43]1803966ae83ee52.png[/img] = 280.25 Hz B: fLs =[img=130x43]1803966af50fda0.png[/img] = 30.6 Hz C: fLs = [img=96x43]1803966aff1bc04.png[/img] = 5585.4 Hz. D: fLs = [img=132x43]1803966b0d87e79.png[/img] = 4.269 Hz.

Calculate the low frequency break point due to the capacitor CS for this BJT amplifier. [img=401x275]1803966add25148.png[/img] A: fLs = [img=98x43]1803966ae83ee52.png[/img] = 280.25 Hz B: fLs =[img=130x43]1803966af50fda0.png[/img] = 30.6 Hz C: fLs = [img=96x43]1803966aff1bc04.png[/img] = 5585.4 Hz. D: fLs = [img=132x43]1803966b0d87e79.png[/img] = 4.269 Hz.

2022-06-29 问题

CLK0接5MHZ的时钟频率，从OUT1输出周期为1秒脉冲信号,则1S= HZ,0.5S= HZ.

2022-06-07 问题

在电力系统正常情况下，工频的频率偏差一般不超过±（）Hz；在非正常情况下，频率偏差不应超过±（）Hz.

2021-04-14 问题

Hearing is the ability to detect _____ and performed by . The human ear can only be sensitive in the range of frequency of _ Hz. to ___ Hz.

Hearing is the ability to detect _______ and performed by ____. The human ear can only be sensitive in the range of frequency of ___ Hz. to ___ Hz.

2022-06-09 问题