This is the 10283rd most frequent Japanese word.
音波
Sound wave.
The word 音波 (sound waves) is used here to describe physical waves consisting of oscillatory movement of air molecules that carry sound.
音波は空気を振動させて広がります。
Sound waves oscillate the air as they propagate.
In this sentence, 音波 refers to the sonar sound waves emitted by dolphins as part of their echolocation and communication.
イルカは音波を使ってコミュニケーションを取ります。
Dolphins use sound waves to communicate.
音波, in this context, refers to ultrasonic sound waves used in medical imaging devices for body examination.