What is Sound
and
What is Noise?

Sound is a form of energy that is transmitted by pressure variations which the human ear
can detect.

When one plays a musical instrument, say a guitar, the vibrating chords set air particles
into vibration and generate pressure waves in the air

A person nearby may then hear the sound of the guitar when the pressure waves are
perceived by the ear. Sound can also travel through other media, such as water or steel.

Apart from musical instruments, sound can be produced by many other sources - man's
vocal cord, a running engine, a vibrating loudspeaker diaphragm, an operating machine
tool, and so on.

Noise is unwanted sound.

Usually the sound of a violin is referred to as music - is something pleasing. Depending
on other factors, the sound may be perceived as noise.

Noise perception is subjective. Factors such as the magnitude, characteristics, duration,
and time of occurrence may affect one's subjective impression of the noise.