这里信号不好。
Generally, because the output voltage signal is very weak, the signal voltage and the noise voltage can't be distinguished.
由于声表面波压电效应产生的电压信号非常微弱，一般放大不能分辨出信号电压和噪声电压。
That's because the phone USES energy searching for a good signal and, if the signal is very weak, trying to get a better connection.
这是因为手机会使用电能寻找耗得信号，如果信号特别弱，还要试着更好地去连接。
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