This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles.

正是由于这种集声，即使是海洋中相对微弱的声音，尤其是低频声音，也能传播数千英里。

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The main effect of these additional observations is a 100-point increase in the frequency count for each response alternative.

这些额外调查对象的主要影响是，使得每个回答情形的频率计数增加了 100 点。

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But some of those precious minutes would be saved by making fewer stops, while train frequency on the traditional west-coast main line will be cut.

但是，这几分钟的宝贵时间将通过减少停靠站的方式节省下来，而传统的西海岸主干线的列车班次会减少。

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The photovoltaic panels generate electricity when exposed to sunlight and are connected to the building's power supply via an inverter synchronised to the electricity main's frequency.

BBC: Solar power for City Works centre in Gloucester

There are two main methods of creating a single-frequency network.

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On channel boosters quickly receive the OTA signal from the main tower and retransmit the signal on the same frequency.

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