These are some questions that come to our mind when we think about “sound“? 

When anything vibrates, it creates sound waves. The loudness of sound depends on the intensity of vibration of the object.. Vibration is the to-and-fro motion of an object. Various activities cause vibration, such as striking, stretching, rubbing, blowing, shaking, rotating, scratching, etc.

• Vibration in the object causes a sound.
• It is the form of mechanical energy.
• Sound needs a medium for propagation. The medium could be any solid, liquid, or gas. Air is the common medium through which the sound travels.
• The sound wave is a longitudinal wave. It means when there is vibration in the molecules, they transfer energy to each-other and move in the direction of the vibration.
• Low pitch sound and high pitch sound have low frequency and high frequency, respectively.

(Frequency, v = 1/T, is defined as the number of completed oscillations per unit time)

(Longitudinal waves: Here, the particle moves in the same direction of wave propagation.)

Factors that affect the nature of propagation of the sound:

• Density and pressure
• The medium through which sound waves travels

In humans, the vibrations are produced by vocal cords. The vocal cord is attached with muscles, which changes the expansion in the cords, and sound is produced. 

We Hear Sound Through Our Ears

The ear converts variations in pressure (in the air) having audible frequency range into electrical signals. These frequencies are transmitted to the brain via the auditory nerve.

• Outer ear: This is known as Pinna which gathers sound from the surrounding. Here, due to compression in the medium, the eardrum starts vibrating which is in the auditory canal.
• Middle ear: Here, vibrations are amplified by three bones, i.e., hammer, anvil, and stirrup.
• Inner ear: Here, the cochlea converts the variations in pressure into electrical signals. These electrical signals are further transmitted to the brain using the auditory nerve. The brain decodes them as sound.