Introduction

People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.

Initiation of Sound Wave

Whenever an entity vibrates, it creates a shock wave, which produces sound. This pressure wave induces vibrational motion throughout the objects in the surrounding medium (air, water, or solid). As particles vibrate, they pass nearby particles, causing the sound to travel farther through the medium. If vibrating air particles vibrate tiny areas of the ear, the human ear senses sound waves. Sound waves are comparable to light waves in several respects. They all come from a specific source and could be spread or dispersed in different ways. Sound waves, unlike light, could only pass through a medium such as air, glass, or metal. This means that in absence of any medium, there would not be any sound. For example, in vacuum there will be no sound, an astronaut in deep space can not talk to each other like they do on the earth surface.

Properties of Sound Wave

Frequency:

Pitch is the consistency that allows one to categories sounds as "higher" or "lower." It offers a tool for arranging sounds based on a frequency scale. Pitch may be translated as the musical expression for frequency, but the two are not synonymous. A high-pitched sound causes molecules to oscillate quickly, while a low-pitched sound causes them to oscillate slowly.

Amplitude:

The relative loudness of a sound wave is determined by its amplitude. The loudness of a note in music is referred to as its harmonic level. In mechanics, the amplitude of sound waves is measured in decibels (dB), which does not correspond to complex values. Shorter amplitudes correspond to softer sounds, whereas longer amplitudes correspond to louder sounds.

Timbre:

The tone color, or "texture," of the sound is referred to as timbre. Different timbres of sounds emit different waveforms, which influence our perception of the sound. The tone color of a piano's sound differs from that of a guitar's sound. This is referred to as the timbre of a signal in physics.

Duration:

 Period in music refers to the length of time that a pitch or tone lasts. They can be classified as long, fast, or take a certain amount of time. The timbre and rhythm of a sound are influenced by the length of a note or tone. In mechanics, the length of a sound or tone starts when it detects and ends when it can no longer be heard.

Velocity:

It tells how fast sound travels in any medium, it travels faster in mediums which have higher density, speed of sound is more in solid than in air. As packed molecules help in transmission of vibration faster, and less losses of energy are there.

Pressure: The local pressure deviation from the ambient atmospheric pressure as a sound wave moves is defined by sound pressure. It is important to understand that sound pressure and air pressure are not the same thing. Air friction has little impact on the speed of sound in general. Sound waves change the vibration encountered by air particles as they travel from the sound source across the air.

Types of Sound Wave

Mechanical sound wave:

In a chain reaction, a sound wave travels across air by replacing air ions. If one particle moves away from its equilibrium location, it pushes or pulls on adjacent molecules, forcing them to move away from their equilibrium positions as well. The noise is carried across the medium as particles begin to replace one another with mechanical vibrations. Sound waves are classified as mechanical waves because of particle-to-particle mechanical interactions of sound conductance. Sound energy, or energy correlated with both the vibrations produced by a vibrating source, involves a medium to move, which renders sound energy a mechanical wave.Air waves, sound waves, electromagnetic waves, and internal water waves are also examples, of mechanical waves of nature that arise as a result of density variations in a body of water. Mechanical waves are classified into three types: transverse waves, longitudinal waves, and surface waves.

Longitudinal sound waves:

A longitudinal wave is the one where the motion of the ions in the medium is parallel to the direction of energy transfer. Shock waves in air and fluids are longitudinal waves since the ions that carry the sound vibrate in a direction opposite to the direction of travel of the sound wave. When you move back and forth, the coils move in back and forth. Analogously, whenever a tuning fork is triggered, the sound wave's trajectory is parallel to the movement of the air particles.

Pressure sound waves:

Since sound waves are made up of compressions and rarefactions, their regions vary from low and high pressure patterns. As a result, sound waves are classified as pressure waves. The human ear, for example, senses rarefactions as low-pressure intervals and compressions as high-pressure periods as it absorbs sound waves from its surroundings.

Transverse wave:

Transverse waves travel with oscillations perpendicular to the wave's path. Since their oscillations are opposite to the direction of energy transfer, sound waves are not transverse waves. Ocean waves are one of the most famous representations of transverse waves. A more concrete example is to move one end of a string up and down while the other end is grounded.

Mechanical sound wave:

In a chain reaction, a sound wave travels across air by replacing air ions. If one particle moves away from its equilibrium location, it pushes or pulls on adjacent molecules, forcing them to move away from their equilibrium positions as well. The noise is carried across the medium as particles begin to replace one another with mechanical vibrations. Sound waves are classified as mechanical waves because of particle-to-particle mechanical interactions of sound conductance. Sound energy, or energy correlated with both the vibrations produced by a vibrating source, involves a medium to move, which renders sound energy a mechanical wave.

Common Mistake

People confuse the direction of wave propagation between transverse and longitudinal waves.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for      

• B.Sc.,
• M.Sc.
• M.tech.