The sound is an organized movement of molecules caused by a body which vibrates within a medium, whether this is water, air, or anything else. The sound is therefore the result of the reciprocating motion a body creates with the speed of its movement. The result is a wave without the transmission of which the sound would be impossible to create.
The human ear is a “mechanical” masterpiece. The way in which it receives and processes the sound waves is unique. It has the ability to hear sounds transmitted between 20Hz and 20,000Hz (Hertz being the unit of measure of sound and it’s practically the vibrations per second created by the sound source).
The frequencies of the modern piano range between 27½Hz for its first note (A1) and 4,186Hz for its last one (C88). This is achieved with the appropriate length and thickness of the strings. Pythagoras suggested that the lengths of the strings can be expressed as ratios of integers thus specifying the proportions of all intervals! Pythagoras’ theories apply to this very day in the construction and tuning of a piano!