Sound - Production and Propagation of Sound

Sound is a form of energy produced by vibrating bodies. A vibration is defined as a rapid back-and-forth motion of an object about its mean position.

Sound requires a material medium (solid, liquid, or gas) for its propagation. It cannot travel through a vacuum because there are no molecules to transmit the vibrations.

Sound travels in the form of longitudinal waves, where the particles of the medium vibrate parallel to the direction of the wave's propagation.

The speed of sound depends on the nature of the medium: $v_{\text{solid}} > v_{\text{liquid}} > v_{\text{gas}}$. For example, the speed of sound in air is approximately $330\text{ m/s}$ to $340\text{ m/s}$, while in steel it is about $5000\text{ m/s}$.

Amplitude ($A$) is the maximum displacement of a vibrating particle from its mean position. It determines the loudness of the sound ($L \propto A^2$).

Frequency ($f$) is the number of vibrations per second, measured in Hertz ($Hz$). It determines the pitch or shrillness of the sound.

Time Period ($T$) is the time taken by a vibrating body to complete one full vibration.

The human audible range of frequencies is from $20\text{ Hz}$ to $20,000\text{ Hz}$ (or $20\text{ kHz}$). Sounds below $20\text{ Hz}$ are called infrasonic, and sounds above $20,000\text{ Hz}$ are called ultrasonic.