Complex Soundwaves/(复合声波) -> #2of3 Intermediate/(中级) -> The Science of Sounds/(声音的科学) -> Learn/(学习)

Complex Soundwaves/(复合声波) -> Generating Sounds/(生成的声音) -> Theory/(理论) -> Step 1 Middle School/(第一步初中) -> Years Group/(年级群)

Complex Soundwaves/(复合声波) -> The Science of Sounds/(声音的科学) -> #2of3 Intermediate/(中级) -> #[Tier 6] Pedagogical Aspects for Children/([第六]教育层为儿童) -> Users Group/(用户群)