Sound Waves

Sound is a mechanical wave, meaning it requires a medium (solid, liquid, or gas) to travel. It cannot travel through a vacuum.

• • Sound is produced by vibrations of objects, which cause vibrations of the particles of the surrounding medium.
  • Thus, sound waves consist of:
    
    • Compressions (C): Regions where particles are closer together, producing higher pressure.
    • Rarefactions (R): Regions where particles are farther apart, producing lower pressure.
  • 

Waveform of sound:

• • Although the particle motion is longitudinal, we often represent sound waves as a transverse wave graphically to show pressure or displacement variations against time or distance.

Important properties of sound waves:

• • Wavelength (\(\lambda\)): Distance between two successive compressions or rarefactions.
  • Frequency (\(f\)): Number of oscillations (vibrations) per second, measured in hertz (Hz).
  • Amplitude (A): Maximum displacement of the particles from their equilibrium position, related to the loudness of sound.
  • Wave speed (v): Given by:
    

    \(v = f \lambda\)

Speed of sound:

• • Sound travels fastest in solids, slower in liquids, and slowest in gases because particle density and elasticity affect the transmission.
  • At room temperature in air: \(v \approx 343 \, \text{m/s}\).

Applications of longitudinal nature of sound:

• Ultrasound scanning: Uses high-frequency longitudinal waves for imaging inside the body.
• Sonar: Uses reflected sound waves in water for detecting objects like submarines or measuring depth.
• Communication: Sound waves carry information in speech, music, and signals.