The Nature of Sound Waves

Waves are everywhere and manifest in different ways. Waves occur when there's a disturbance in a system, and that disturbance travels from one place to another.

There are two main kinds of waves:

• Mechanical waves: Need a medium to travel (e.g., sound, water waves).
• Electromagnetic waves: Can travel through a vacuum (e.g., light, radio waves).

Mechanical waves are classified into three groups based on the direction of particle motion relative to wave movement:

• Longitudinal waves: Particles move back and forth in the same direction as the wave.
• Transverse waves: Particles move back and forth at right angles to the wave motion.
• Combined waves: A combination of longitudinal and transverse waves (e.g., sea waves).

Sound waves are represented as sine waves characterized by:

• Speed of sound: Speed at which the wave propagates.
• Wavelength (λ): Distance between corresponding points of the wave.
• Frequency (f): Number of wave repetitions per unit time (Hz).

The relationship between wavelength, speed, and frequency is given by:

λ = v / f

Where:

• λ = Wavelength
• v = Speed of sound
• f = Frequency

Frequency determines pitch, while wavelength relates to the size of musical instruments. High-frequency sounds have short wavelengths, and low-frequency sounds have long wavelengths.

Human hearing ranges from 20 Hz to 20,000 Hz. Sounds outside this range include:

• Infrasound: Below 20 Hz (e.g., elephant communication, earthquakes).
• Ultrasound: Above 20,000 Hz (e.g., medical imaging, animal communication).

The speed of sound varies by medium and is influenced by factors like temperature and material density. Examples:

• Air (20 °C): 343 m/s
• Water (20 °C): 1481 m/s
• Aluminium: 6420 m/s