FIRST, What is Sound?

Sound is evident in our everyday life. Imagine what life would be without sound! Seldom do we delve into the depths of what sound really is and the ways in which sounds are produced, propagated and detected. Do we really know what sound means? 

Sound is a wave that is created by vibrating objects placed in a medium. By vibrating the object in the medium, shifting of layers of the particles of the substance occurs, and as such longitudinal sound waves are produced by it (air molecules vibrate parallel to the direction of wave motion). Thus particles and therefore a medium is required for sound waves to transmit. Also, the speed of sound differs in gaseous, liquid and solid mediums.

  Indeed, sound is a wave. Almost all of us would think of the sea when the word “waves” comes out. However, waves are more than just the sea. In actual truth, waves are made up of periodic motion - motion made up at regular intervals. It can also be thought of a travelling disturbance, transferring energy from one place to another. The origin of any wave is the vibration or oscillation. This causes a wave motion, the propagation of a wave, which can be seen in waves in a ripple tank.

There are two types of waves. 

1) Transverse waves- direction of wave motion is perpendicular to the direction of vibration. Examples include a ripple in a pond, and waves on a string. 
2) Longitudinal waves- where the direction of the wave motion is parallel to the direction of vibration. Examples include tsunami waves and sound waves.

 A sound wave comprises of a series of compressions and rarefractions in a medium. Compressions are regions where air pressure is slightly higher than the surrounding air pressure and rarefractions are regions where air pressure is slightly lower than the surrounding air pressure. Also, waves transfer energy and not matter. For example, sound waves disturb the surrounding air particles which then disturb neighbouring particles. The air does not move collectively, instead, pressure, momentum and kinetic energy is transferred as gaseous molecules collide elastically. 

The speed of sound of in a gas is affected by temperature and humidity. With an increase in temperature, the speed of sound in a gas increases. Similarly, when humidity rises, there are more water molecules in the air, and thus sound travels faster.

Volume and pitch is distinctive to each sound. Pitch is related to the frequency of the sound wave. The higher the frequency of the sound wave, the higher the pitch. Volume is related to the amplitude of the sound wave. The higher the amplitude, the greater the volume.

Graph Describing a Longitudinal Sound Wave

Wavefronts are the surfaces associated with a propagating wave and passing through all points in the wave that have the same phase. In the event that velocity of sound is to be calculated, the equation: Velocity = frequency x wavelength is used.

Here is a video provided for a concise summary on SOUND! :)