The transmission of sounds is best in __________ and __________, whereas they are the worst in __________ and __________.

• A. Copper, Steel; Asbestos cement, Concrete
• B. Copper, Asbestos cement; Steel, Concrete
• C. Steel, Concrete; Copper, Asbestos cement
• D. Asbestos cement, Concrete; Copper, Steel

Answer: (A)

Sound travels through solids by vibrating the material itself. Materials that are stiff and relatively dense let those vibrations propagate with less energy loss, so metals like copper and steel transmit sound along a pipe more readily. In contrast, asbestos cement and concrete have more internal damping and a heterogeneous, porous structure that scatter and absorb vibrational energy, causing greater attenuation of sound. That combination makes transmission strongest in copper and steel and weakest in asbestos cement and concrete.