Which of the following isn't an example of noise?

Sound is a type of mechanical energy that may be transferred through many materials. For instance, musical instruments, a man's voice chord, and so on.

A sound that is unpleasant or loud and causes a disruption is referred to as noise. Noise can be created by explosions, factories, automobiles, or a blend of many voices.

Music is the outcome of a combination of multiple frequencies resulting in an organized sound. - A musical instrument's sound is an example of music. As a result, the sound of musical instruments is not considered noise. 

 Hence, option 4 is right.