Sound Waves: Vibrations, Production & Wave Mechanics

15 Dec 2023

Sound Waves: Vibrations, Energy, and the Art of Hearing

Everyday we hear sounds from various sources like humans, birds, bells, machines, vehicles, televisions, radios etc. Sound is a form of energy which produces a sensation of hearing in our ears. Sound is produced by vibrating objects. When an object vibrates, it creates a disturbance in the surrounding air molecules, generating a sound wave.

Production of Sound: Vibrations, Waves, and the Human Voice

  • Production of Sound: Sound is produced by striking the tuning fork, by plucking, scratching, rubbing, blowing or shaking different objects. 
    • We set the objects vibrating and produce sound. 
  • Meaning: Vibration means a kind of rapid to and for motion of an object. 
  • Sound Production in Human: The sound of the human voice is produced due to vibrations in the vocal cords. 
    • Sound is produced by the vibration of objects. 
  • Wave Propagation: When an object vibrates, it creates a disturbance in the surrounding medium (usually air) which propagates in the form of waves, ultimately reaching our ears.
Voice box in humans
Voice box in humans

Production of Sound by Humans: The Role of the Voice Box and Vocal Cords

  • In humans, the sound is produced by the voice box or the larynx
    • Voice box in humans  is at the upper end of the windpipe. 
    • Two vocal cords are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air. 
  • When the lungs force air through the slit, the vocal cords vibrate, producing sound. 
    • When the vocal cords are tight and thin, the type or quality of voice is different  from that when they are loose and thick.

Propagation of Sound: Vibrations, Mediums, and Wave Dynamics

  • Sound is produced by vibrating objects. 
  • Required Medium: The matter or substance through which sound is transmitted is called a medium. 
    • It can be solid, liquid or gas. 
    • Sound moves through a medium from the point of generation to the listener.
  • When an object vibrates, it sets the particles of the medium around it vibrating. 
    • The particles do not travel all the way from the vibrating object to the ear. 
    • A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position. 
    • It then exerts a force on the adjacent particle. 
    • As a result, the adjacent particle gets displaced from its position of rest.
  • After displacing the adjacent particle, the first particle comes back to its original position. 
    • This process continues in the medium till the sound reaches your ear. 
    • The disturbance created by a source of sound in the medium travels through the medium.
  • Wave: It is a disturbance that moves through a medium when the particles of the medium set neighbouring particles into motion.
  • Mechanical Wave: Sound waves are characterised by the motion of particles in the medium and are called mechanical waves. 
    • Air is the most common medium through which sound travels. 
compression
A vibrating object creating a series of compressions (C) and rarefactions (R) in the medium.
  • Compression: When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure. This region is called a compression (C).
    • This compression starts to move away from the vibrating object.
  • Refraction: When the vibrating object moves backwards, it creates a region of low pressure called rarefaction (R) . 
  • As the object moves back and forth rapidly, a series of compressions and rarefactions is created in the air. 
  • These make the sound wave that propagates through the medium.

Sound Waves are Longitudinal waves: Longitudinal Motion and Wave Nature

  • Longitudinal Waves: In a longitudinal wave, the particles of the medium (such as air, water, or solids) vibrate in the direction of the wave’s propagation. 
    • This means that the motion of the particles is parallel to the direction of the wave itself.
    • In the case of sound waves, air molecules move back and forth parallel to the direction in which the sound is travelling. 
    • The compressions and rarefactions alternate, creating a series of high-pressure (compression) and low-pressure (rarefaction) regions.
  • Transverse Waves: In a transverse wave, the particles of the medium oscillate perpendicular to the direction of the wave’s motion. 
  • This creates crests (high points) and troughs (low points) in the wave.
    • Examples of transverse waves include light waves and waves on a string. 
    • In light waves, the electric and magnetic fields oscillate perpendicular to the direction of propagation.
  • Nature of Waves: While sound waves are longitudinal, some waves in other mediums (like water waves on the surface of a pond) can exhibit both longitudinal and transverse characteristics. 
  • Surface Waves: These are known as surface waves, as they have components that move both parallel and perpendicular to the direction of wave motion. 
  • Longitudinal Wave Only: Sound waves specifically, which travel through air or other mediums, are longitudinal waves and do not exhibit transverse motion.

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UDAAN PRELIMS WALLAH
Comprehensive coverage with a concise format
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Designed as per recent trends of Prelims questions
हिंदी में भी उपलब्ध

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