sound

Introduction
Plane waves
- Wavelength, period, and frequency
- Amplitude and intensity
  - Mathematical values
  - The decibel scale
- The speed of sound
  - In gases
  - In liquids
  - In solids
Circular and spherical waves
- Attenuation
  - The inverse square law
  - Sound absorption
- Diffraction
- Refraction
- Reflection
- Impedance
  - Impedance mismatch
  - Acoustic filtration
- Interference
  - Constructive and destructive
  - Beats
- Moving sources and observers
  - The Doppler effect
  - Shock waves
Standing waves
- In stretched strings
  - Fundamentals and harmonics
  - Overtones
  - Mersenne’s laws
- In air columns
  - Open tubes
  - Closed tubes
  - Measuring techniques
- In solid rods
- In nonharmonic systems
  - The Helmholtz resonator
  - Rectangular boxes
  - Stretched membranes
Steady-state waves
- Spectral analysis
  - The Fourier theorem
  - The sound spectrograph
- Generation by musical instruments
  - Bore configuration and harmonicity
  - Other effects on tone
  - Variations in air pressure
- The human voice
- Noise
Hearing
- Dynamic range of the ear
- The ear as spectrum analyzer
- Binaural perception

References & Edit History Related Topics

Images & Videos

Watch a suspended vibrating spring to learn about the propagation of sound waves

graphic representations of a sound wave

How to measure a wave: frequency and period explained

Understanding frequency and amplitude in sound

Huygens' principle

acoustic filters typically used in air-handling systems

first three harmonic standing waves in a stretched string

first 10 notes in the overtone series of G2

first three harmonic standing waves in open and closed tubes

Helmholtz resonator

For Students

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sound: Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Last Updated: Nov 05, 2025

Photos and Videos

graphic representations of a sound wave

Huygens' principle

acoustic filters typically used in air-handling systems

first three harmonic standing waves in a stretched string

first 10 notes in the overtone series of G2

first three harmonic standing waves in open and closed tubes

Helmholtz resonator

Fourier synthesis of a complex wave

lightning and thunder

Watch a suspended vibrating spring to learn about the propagation of sound waves

How to measure a wave: frequency and period explained

Understanding frequency and amplitude in sound

How does the McGurk effect trick your brain?

Understanding wave interference through sound experiments

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Topics

acoustical shadow monaural sound hypersound echo sound localization filtration specific acoustic impedance pitch acoustic absorption reverberation electromagnetic radiation wave gravitational wave seismic wave longitudinal wave standing wave transverse wave bow wave radio wave elastic wave

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Key People

Helmholtz.

Hermann von Helmholtz

German scientist and philosopher

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Eric Zepler

German-born physicist

Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.

All About Physics Quiz

Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.

Physics and Natural Law