Sound Wave

Sound Wave

Sound waves are the propagation of disturbance of particles of medium in a wave-like pattern produced by vibrating bodies such as vibrating diaphragms. Its unit of measurement is Decibels.

Sound Wave

Sound is the movement of acoustic waves producing some good or bad noise. Sound propagates in waves-like movements. We humans can only hear sound ranging from 20Hz to 20KHz. Above which are called ultrasonic sounds and below 20Hz it is called infrasonic. Few animals such as elephants, rhinoceros, and hippopotamus can hear infrasonic sounds because the structure of their ear is quite different from humans and they are large. And some animals like beetles, dogs, dolphins, etc. can hear and communicate between them in ultrasonic sound waves. 

What is a sound wave?

Sound waves definition says it as waves of compression and rarefaction in which disturbance of particles (sound) moves in the air or other elastic media. 

Depending on hearing of sound waves in humans and other animals’ cases, sound can be said as a stimulus. It stimulates the movement of our eardrums to produce some sound that is detected and analyzed by our brain. In simple words, sound waves can be said to be a sensation. 

The SI unit to measure sound in dB (decibels). It is named in the honor of Alexander Graham Bell who also invented the telephone and audiometer. 

Physics behind the generation of sound waves

For the creation of sound waves, there are sound sources such as a vibrating diaphragm or other vibrating body. Which then vibrates and disturbed the particles of the medium such as air or water or solid. A medium is necessary for sound to travel from one place to another. As a result, sound cannot travel over space. So, then when the nearest particle is disturbed that disturbance in the medium is propagated to some distance based on the strength of disturbance. And the frequency and wavelength of the wave are generated by the amount or frequency of the diaphragm’s vibration. Point to be noted that only the movement of energies of particles takes plane not the particles. 

In mediums like water and air sound waves travel in the longitudinal direction, however, they are solid, they travel in the transverse direction. 

Sound Waves are affected by 

Sound waves are directly dependent on the property of the medium they travel. Therefore, they can get affected by the density, pressure, speed, temperature, and other properties of the medium. 

Another property that can affect sound waves is the motion of the medium. If the medium particles themselves are moving in the direction of sound or in the direction opposite to sound. They can alter the absolute speed of sound. 

The viscosity of the medium also affects the sound waves. As they are the property of the medium itself. 

Characteristics of Sound Waves

Similar to other waves, sound waves can be characterized as their wavelength, time-period, frequency, amplitude/pitch, and speed or velocity.

  • Wavelength: It is the distance between two troughs or two crusts. 
  • Amplitude/pitch: It is the distance between the mean line and trough or the crust. 
  • Frequency: It is the number of waves that pass through a particular point at a particular time. 
  • One Wave: It is the combination of one trough and one crust. 
  • Speed: The distance traveled by one wave in a particular time such as in one minute or one hour is called the speed of the sound. 
  • Time-period: It is the time required to produce one wave. 

Speed of Sound

Speed of sound is a fundamental property of the material. Therefore, it depends on the type of material and the temperature of the medium. It is given by,


a = speed of sound

Y = Ratio of specific heat

R = Gas Constant

T = Absolute Temperature

When any object travels at a greater speed than the speed of sound it is called to be in ultrasonic speed. Some of those bodies are high-speed airplanes like fighter planes and research-purpose planes. They create sonic booms when they pass the speed of sound and also create shock waves. A shock wave is a pressurized region produced by the disturbance in air or other mediums by anybody. And the sonic boom is a loud explosive sound produced by an object when it passes through the air with a speed greater than the speed of sound.


To sum up, sound waves are the disturbance produced in an elastic medium by any vibrating body which propagates in the form of a wave-like movement. A sound wave is affected by the properties of the medium such as temperature, density, pressure, etc. And an elastic medium is a must for a sound wave to travel. Since space does not have any medium, therefore, we cannot hear any sound in space. Sound waves are used in various industries and daily uses. Such as the loud ringing of phones for alarming people about a phone call. In industries like detecting cracks in solids, ultrasound is used for medical purposes to help deliver drugs in the body and to monitor chronic liver disease. Similarly in other industries too.