There are three fundamental characteristics of musical sound. They are as follows:
2. Quality or timber
3. Loudness or intensity
1. Pitch: The shrillness or sharpness of sound is called the pitch of the sound. The sound with high pitch is shrill while the sound with low pitch is sharp. The pitch of the sound depends upon the frequency of the note produced from the musical instruments or sound producers. The voice produced by women, mosquito, children etc is shriller and has low pitch. However, the voice of the old man, buffalo etc is hoarse and has high pitch.
2. Quality or timber: The measure of complexity of the sound that helps us to distinguish between two notes of same pitch or loudness is called quality or timber. Timber depends upon the wave form of the sound. We can distinguish the sound of two different friends, different musical instruments without seeing through timber. The number of overtones and harmonics present in the note determines the quality or timber and thereby quality of sound.
3. Loudness or intensity: The loudness of the sound is the degree of sensation produced in the ear which depends upon the hearing sensitivity of the listener. The unit of loudness is phon. The loudness varies with the frequency and intensity of the sound.
The intensity of the sound wave at a surface is the average rate per unit area at which energy is transferred by the wave throughout the surface. So,
I = P/A
Where, P is the rate of transfer of energy also called power of the sound wave and A is the area of the surface intercepting the sound. The unit of I is W/m2.
Loudness and intensity of sound depends upon several factors mentioned below:
- Amplitude of the vibration of the source
- Motion of the medium
- Presence of other body
- Surface area of the vibrating body
- Frequency of the sound
Threshold of hearing
The lowest intensity of the sound that is heard by human ear is called thrasehold of hearing. The magnitude of hearing sensation depends upon both the intensity and frequency of the sound. The threshold of hearing is represented as Io.