Physics of Sound

Sound and Waves

• Sound is a form of mechanical energy that produces the sensation of hearing through vibrations of different objects.
• It travels in the form of waves, requiring a material medium to propagate, which can be solid, liquid, or gas.

Propagation of Sound

• Sound waves can be considered the propagation of pressure or density variations in the medium, resulting in a series of compressions and rarefactions.
• A compression (C) is a region of compressed air with increased density or pressure, while a rarefaction (R) is a region of rarefied air with decreased density or pressure.
• A vibrating object produces a series of compressions and rarefactions in the medium, with the sound energy traveling in the medium, not the particles themselves.

Types of Waves

• Mechanical waves are periodic disturbances that require a material medium for propagation, including sound waves, water waves, and waves produced in stretched strings and slinkies.
• There are two types of mechanical waves: transverse waves and longitudinal waves.
• Transverse waves have individual particles moving in a direction perpendicular to the direction of propagation.
• Longitudinal waves have individual particles moving in a direction parallel to the direction of propagation, which includes sound waves.

Characteristics of Sound Waves

• Wavelength (λ) is the distance between two successive crests or troughs, measured in meters (m).
• Time period (T) is the time taken by two consecutive compressions or rarefactions to cross a fixed point, measured in seconds (s).
• Frequency (𝛎) is the number of compressions or rarefactions per unit time, measured in Hertz (Hz).
• Speed (v), wavelength (λ), and frequency (𝛎) are related as v = λ𝛎.
• Amplitude is the magnitude of the maximum displacement of a particle from its mean position.