Sound Vibration Propagation of Sound


Sound is created when any material vibrates and propagates through a medium for creating sound waves. It is defined as a form of energy and important senses of the human body. Some vibrations are clearly visible and some are not. The object placed to the vibration distracts the particle's state of equilibrium in a particle media and vibration constantly transfigures from one particle to the other. Vibration is defined as the periodic motion of back and forth of the elastic body's particles or medium. Sound is a sequence of pressure waves, which is transmitted through a compressible medium.

What are sound waves?

Sound is demonstrated as the vibration that helps in propagating as an acoustic wave through a conveyance medium such as solid, liquid or gas. Sound waves are referred to as longitudinal waves (Errico et al. 2020). The waves of sound are produced by the vibrations of the object and create pressure waves such as ringing cell phones.

Sound waves

Figure 1: Sound waves

The pressure waves disordered the particles in the medium of their surroundings and those particles often distract the others. The disturbance pattern makes the outward movement in a certain pattern of waves like the ocean or sea (Kapoor et al. 2021). The sound waves carry the energy of sound through the medium in different directions and less intensely shift further from a source.

Characteristics of sound waves

Sound waves possess mainly five characteristics which include "amplitude", "frequency", "velocity", "wavelength" and "time".


The most essential feature of sound waves is wavelength. Sound comprises a longitudinal wave that consists of refractions and compressions as they advance through a particular medium (Xu et al. 2020). The distance that one wave progresses before it repeats is the wavelength.


The velocity of the wave is mentioned as the speed. It is determined as the distance in meters per second that a wave progresses in one second.

Propagation of sound

Figure 2: Propagation of sound


The amplitude is mentioned as the size of the provided wave. The amplitude of the sound wave or propagation of sound is more accurate. It is explained as the highest particle displacement distracts the sound waves as it moves through a medium.


The frequency is mentioned to the sound waves' numbers, a sound created per second. The sound of low frequency possesses fewer waves whereas the sound of high frequency has more (Raghuvanshi & Snyder, 2018). Sound frequency is calculated in hertz (HZ) which is not reliant upon the sound medium which is passing through.


The time-period is referred to as contrasting to the frequency. It is the time that is necessary to create a single complete cycle or wave. Every vibration of the vibrating body creating the sound is similar to that of waves.

Speed of propagation of sound

The travelling of sound is demonstrated as the propagation of sound. Sound is often propagated by the "fro and to" motion of the medium particles. The particles around any certain medium vibrate when any objects vibrate (Curthoys et al. 2019). Sound needs a medium for propagation. The particles in the touch of contact with the object of vibration are first displaced from the position of equilibrium.

Experiment of bell-jar for sound propagation

Figure 3: Experiment of bell-jar for sound propagation

Sound requires a medium of material like steel, water or water for its transmission. Sound cannot pass through a vacuum and it cannot be demonstrated by the experiment of Bell-Jar. Considering the experiment of Bell and Jar where an airtight glass jar and electric bell are taken. The electric bell is draped inside the jar. From the above figure, the jar is attached to the vacuum pump (Brainkart, 2022). People can heat the bell sound in case the bell is created to ring. The air inside the jar is electrified gradually and the sound gets feebler when the glass jar is taken away from the vacuum pump. Sound cannot be audible if the air is completely cleared from the glass jar.

Factors impacting the speed of sound

The sound speed relies on the elasticity and density of the medium through which it passes. Sound travels faster in liquids in comparison to gases (Şahinoğlu & Rafighi, 2020). It is more rapid in solids than in the other two mediums.

Sound created by a vibrating body

Figure 4: Sound created by a vibrating body

Certain factors cause the flow of sound to slow in gases. The factors that impact the speed of sound in gases are the impact pressure, temperature, the density of the gas, humidity, amplitude, wind and change in frequency of acoustic waves.

Medium Sound waves speed (meter per second)
Dry air 349
Water 1437
Glass 4540
Aluminium 6320
Wood 3850

Table 1: Speed of sound in different media


Sound is a kind of energy that is made by vibrating materials. The waves of sound are created when the vibrating body generates the medium around it to vibrate. Wave movement is often referred to as propagation in the physical world. Propagation medium requires the medium to be elastic, frictionless and must have inertia. Temperature and density of the medium impact the sound propagation. Waves may be "reflected", "refracted" or "attenuated by the medium" during their propagation through a solid medium.


Q1. What are the types of sound waves?

Sound waves basically come under three categories namely mechanical waves, longitudinal waves and pressure waves. The waves that are below 20Hz known to be infrasonic and the frequency above 20000 Hz are termed Ultrasonic waves.

Q2. What energy is known to be sound vibration?

Sound energy is the consequence when a force either pressure or sound, creates a substance or an object to vibrate. The energy gets shifted through that object in waves. Those forms of sound waves are mentioned to be Kinetic mechanical energy.

Q3. Does sound transmit through the air?

Sound transmits through the air or different mediums as a form of a longitudinal wave. The sound in longitudinal waves has the mechanical vibration that comprises happenings of the wave along the propagation direction of the wave.

Q4. Why is the sound speeding the highest in solid?

The sound speed is highest in a solid medium because the molecules are nearer together. It permits the waves of sound to travel more rapidly through it.



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Errico, F., Franco, F., De Rosa, S., Petrone, G., & Ichchou, M. (2020). Aeroelastic effects on wave propagation and sound transmission of plates and shells. AIAA Journal, 58(5), 2269-2275. Retrieved from:

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Xu, Z., He, W., Xin, F., & Lu, T. J. (2020). Sound propagation in porous materials containing rough tubes. Physics of Fluids, 32(9), 093604. Retrieved from:


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Updated on: 21-Aug-2023


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