Key Concepts: Nature of Sound Waves

What is Sound?

• Sound is a longitudinal mechanical wave — it requires a medium (solid, liquid, or gas) to travel.
• Sound cannot travel through a vacuum.
• Sound waves consist of compressions (high pressure) and rarefactions (low pressure).

Production and Detection

• Sound is produced by vibrating objects (vocal cords, speakers, tuning forks).
• Detected by the ear (eardrum vibrates) or by microphones (diaphragm vibrates).

Properties

• Sound waves can be reflected (echoes), refracted, diffracted, and can interfere.
• Human hearing range: approximately 20 Hz to 20,000 Hz.
• Below 20 Hz: infrasound. Above 20,000 Hz: ultrasound.