Loudness of sound is determined by:

Amplitude of the vibrating body

The loudness of sound is determined by its amplitude. The greater the amplitude of vibration, the louder the sound is perceived.

Detailed Explanation:

1. What is Loudness?
   Loudness is a measure of how strong or intense a sound appears to the human ear. It is a subjective quality because it varies based on the listener's sensitivity.
2. Role of Amplitude in Loudness:
   • The amplitude of a sound wave refers to the maximum distance a vibrating particle moves from its mean position.
   • A larger amplitude produces stronger air vibrations, resulting in louder sounds. For example, when the cone of a loudspeaker vibrates over a longer distance, the air disturbance increases, leading to a louder sound.
3. Mathematical Relation:
   The loudness of sound is proportional to the square of the amplitude. If the amplitude doubles, the loudness increases fourfold.
4. Soft vs. Loud Sounds:
   • When the amplitude is small, the sound is soft.
   • When the amplitude is large, the sound is loud.