Telephone & Stethoscope

[quarky]

(1) Toy telephones are constructed by connecting 2 plastic cups with a long string. How does sound transmission occurs when the string is pulled taut from one cup to the other?
(2) How does a stethoscope works? Through what medium does sound travel?

[e(ho0n3]

(1) Think vibrations.
(2) Think vibrations again. Sound travels through any medium possessing mass. Why? Because an object possessing mass can vibrate. Empty space can't vibrate so that means no sound can travel through empty space.