Their instruments detected very faint radio waves at a frequency of 3 kilohertz.
他们的仪器探测到了频率为3千赫的非常微弱的无线电波。
《柯林斯英汉双解大词典》
2
When their stems were cut, the plants started "screaming" between 20 and 100 kilohertz, and the scientists guess that this scream is probably meant to warn other plants nearby.