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  1. Glossary
  2. /Physics
  3. /Sound

What is Sound?

In short

Sound is a wave produced by a vibrating object. It travels through a material as alternating compressions and rarefactions, and it needs a medium to travel in.

In simple words

When a guitar string vibrates, it pushes the air into compressions (higher pressure) and pulls it into rarefactions (lower pressure). These pass on as a longitudinal wave. Sound cannot travel through a vacuum. Its speed is about 343 m/s343\ \text{m/s}343 m/s in air at 20∘C20^\circ\text{C}20∘C, higher in liquids and highest in solids. The ear detects sound between about 20 Hz20\ \text{Hz}20 Hz and 20 000 Hz20\,000\ \text{Hz}20000 Hz.

Example

Thunder is heard 3.0 s3.0\ \text{s}3.0 s after lightning is seen. The distance to the storm is about 343 m/s×3.0 s=1.0 km343\ \text{m/s} \times 3.0\ \text{s} = 1.0\ \text{km}343 m/s×3.0 s=1.0 km, since light arrives almost instantly.

Also searched as: how is sound produced, rarefaction of air, human hearing, what is wavelength of sound.

Learn it properly

  • Lessons on this topic
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Related terms

  • Wavelength
  • Frequency
  • Amplitude

← All glossary terms

Learn it in

  1. How Sound Is Made and How It TravelsClass 9 to 10
  2. Echoes, Hearing and UltrasoundClass 9 to 10
  3. Beats, Resonance and the Doppler EffectClass 11 to 12
All lessons on this topic →

Practise

  1. A vertical glass tube 1.20 m tall, with an inner radius of 2.5 cm, is full of water to…Hard
Fork A gives its first resonance at 20.8 cm in a tube, and the second resonance is 43.0…Hard
  • The speed of sound in air is 331 m/s at 0 °C, and it grows with the square root of the…Medium
  • A resonance tube 1.0 m long has an inside diameter of 3.8 cm…Medium
    • All problems on this topic →

    Quick questions

    1. An organ pipe has two neighbouring resonant frequencies of 500 Hz and 700 Hz, and no…Hard
    2. A container holds a mixture of 1.0 mol of helium (4 g/mol) and 1.0 mol of oxygen (32…Hard
    3. A source moves straight towards a listener who stands still, and the listener hears…Hard

    More Physics terms

    1. Acceleration
    2. Acceleration Due to Gravity (g)
    3. Adiabatic Process
    4. Angle of Incidence
    5. Angle of Reflection
    6. Archimedes' Principle
    All Physics terms →

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