For general exploringobjects requirement, narrow pulse signal with tens millimicro second to millimicrosecond has the frequency spectrum from DC to thousands MHz.
按照对地目标
的一般需要,通常


到十
量级的电

窄脉冲,信号频谱具有从直流低频直到千兆赫兹的宽带。
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Our ears are most sensitive to sound, where most of the information in speech is contained, and that's between about 500 hertz and 2 kilohertz, which is somewhere between the middle and the upper three-quarters of a piano keyboard.
我们的耳朵对声音最敏感的地方是大多数语音信息所在的地方,大约在 500 赫兹
2 千赫兹之
,这大约是在钢琴键盘的中

四分之三之
。
-科学美国人 2021年11月合集