Sound Wave

 *sound science series # 1 

The nature of a sound wave: Sound is a Mechanical Wave; Sound is a Longitudinal Wave; Sound is a Pressure Wave.

Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing.

• Sound waves are characterized by the motion of particles in the medium and are called mechanical waves.     

• Waves are created due to: 

1. Compression - region of high pressure or density and
2. Rarefaction - region of low pressure or density.

• Pressure is related to the number of particles of a medium in a given volume.
• Propagation of sound can be visualized as propagation of density variation or pressure variation in the medium.
• These waves are called longitudinal waves. In these waves the individual particles of the medium move in a direction parallel to the direction of propagation of the disturbance. The particles do not move from one place to another but they simply oscillate back and forth about their position of the rest. This is exactly how a sound wave propagate, hence sound waves are longitudinal waves.

 Wavelength: The distance between two consecutive compression (C) or two consecutive refraction is called the wavelength. 

•  Wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves.
•  Wavelength is commonly designated by the Greek letter lambda (λ): The SI unit of wavelength is the meter.

wavelength

  
Wave packet: A wave packet refers to the case where two (or more) waves exist simultaneously. A wave packet is often referred to as a wave group.

•  A composition of several waves of different wavelength can produce a wave packet. 
•  The average wave is also called the carrier wave. 
•  This situation is permitted by the principle of superposition. This principle states that if any two waves are a solution to the wave equation then the sum of the waves is also a solution. This principle holds only for linear systems.

A wave packet

  
A simple experiment demonstrating that sound waves need a medium to travel:

                                                                 

a simple experiment to show that sound needs a medium to travel

*Note: all pictures thankfully shared from various sources..