2.1 声音的产生与传播
优酷:https://v.youku.com/v_show/id_XNTk4MTgzMjkwOA==.html
2.2声音的特性
优酷:https://v.youku.com/v_show/id_XNTk4MTgzMDExMg==.html
2.3声的利用
优酷:https://v.youku.com/v_show/id_XNTk3OTY5MzQ3Ng==.html
2.4噪声的危害和控制
优酷:https://v.youku.com/v_show/id_XNTk3OTY5MzQ5Mg==.html