Musical Sound in Physics:
The sound produced due to regular and periodic vibrations that are pleasing to hear is called musical sound.
Noise:
The sound produced by an irregular or shortlived vibration is called noise.
Example: The explosion of a cracker, firing of a gun, etc.
Tone:
Musical sound of a single frequency is called a tone. When the source of sound vibrates in SHM, it produces a tone. The two prongs of a tuning fork vibrate in SHM and produce the sound of a single frequency. Thus, the sound of a tuning fork is a pure tone.
Note:
Musical sound due to a mixture of more than one frequency is called a note. The sound produced by different musical instruments consists, in general, of more than one tone. If a tone is compared with monochromatic light such as red light, a note can be compared with compound light. The tones within a note are classified on the basis of their frequencies:
1. Fundamental Tone: The tone with the lowest frequency present in a note is called the fundamental tone.
2. Overtones: The tones in a note, other than the fundamental tone are called overnotes.
3. Harmonics: Harmonics are tones having frequencies that are integral multiples of that of the fundamental tone. The fundamental tone is also harmonic.
4. Octave: A tone whose frequency is twice that of the fundamental tone is said to be the octave of the fundamental tone.
Characteristics of Musical Sound:
There are three characteristics of musical sound which differentiate musical notes. These are loudness, pitch, and quality.
1. Loudness: It is related to the sound energy reaching our ears per unit of time. If the sound energy reaching our ears in 1 second goes up, we perceive a corresponding increase in the loudness.
2. Pitch: It is that characteristic that differentiates a sharp or a shrill sound from a grave one. It increases with the increase in frequency of the source.
3. Quality or timbre: It is that characteristic of a musical note within that enables us to distinguish between a note emitted by one musical instrument from a note of the same loudness and pitch emitted by another instrument. It depends on the number of overnotes present in a note and their relation with the fundamental tone.