This is the 554th most frequent Chinese word.
波
"Wave" or "ripple".
The word '波' in this sentence refers to 'waves' in a physical sense, specifically water waves on the sea.
海上的波浪非常壮观。
The waves on the sea are very spectacular.
Here '波' refers to 'waves' in a more abstract sense, the oscillations or disturbances in the air that carry sound.
声音通过空气产生的波传播。
Sound propagates through waves created in the air.
In this usage, '波' is part of '波动', meaning fluctuations or undulations, indicating changes or instability.