【全集原版 美國中小學 課程全套 社會+自然科學+詞彙等】外教 Brian Stuart 精講 英語口語 聽力 學英語的同時獲取海量科學知識 P200 - 200 【Level D】001 A Dream Job

This lesson from Science Book 3 focuses on the fundamentals of sound waves. It explains how sound is created as energy, how it travels through different mediums, and the biological and physical processes—such as vibration and reflection—that allow humans to perceive sound and experience phenomena like echoes.