Musical Sound in Physics:
The sound produced due to regular and periodic vibrations that are pleasing to hear is called musical sound.
The sound produced by an irregular or shortlived vibration is called noise.
Example: The explosion of a cracker, firing of a gun, etc.
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.
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.