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. Click on the demo buttons and you will hear the noise from different sources.
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.