The distance at which a sound can be heard depends on its intensity. Intensity is the average rate of flow of energy per unit area perpendicular to the direction of propagation, similar to the rate at which a river flows through a gate in a dam.
- intensity [inˈtensiti] n. 强度
- flow [fləu] n. 传播
- perpendicular [ˌpə:pənˈdikjulə] adj.垂直的
- dam [dæm] n.坝
