Sound

Sound:

Sound: 

It is a wave which is produced by vibrations of bodies.
It is a mechanic wave. It needs a medium to travel i.e air
It is a longitudinal wave. 
It cannot travel in vacuum.
Its speed in air is about 330m/s


Wave-
A wave is a disturbance that travels through space and time, usually accompanied by the transfer of energy.

Types of waves-
1. Mechanical waves
2. Non-Mechanical waves

1. Mechanical waves-
 The type of waves which need a medium to travel is known as MECHANICAL WAVE.
Eg- Sound

2. Non-Mechanical waves-
The type of wave which do not need a medium to travel is known as NON-MECHANICAL WAVE.

Frequency(F)- 
Frequency is defined as number of oscillation per second.
It's Unit is Hertz(Hz)

Amplitude-
Amplitude is maximum displacement between two consecutive crust & trough.
Its Unit is meter(m)

Time Period(λ)
Time Period is the time required to complete one oscillation.
Its Unit is second(s)
T= 2
λ means lambda


Relation between Time period & Frequency
F = 1/T
v = Distance/Time
Here Distance is Wavelength(λ)
Here Time is Time period.(T)
Therefore
v = λ/T
  As T=1/F
v = λ/1/F
   = λF

How do we hear?

The shape of the outer part of the ear is like a funnel. When sound enters in it, it travels down a canal at the end of which a thin membrane is stretched tightly. It is called the  eardrum. It performs an important function.The eardrum  is  l ike a st retched rubber sheet. Sound vibrations make the eardrum vibrate . The eardrum sends vibrations to the inner ear. From there, the signal goes to the brain. 

Noise & Music-
Noise -
 Noise is unpleasant sound. 
It is caused by irregular vibration.

Music-
Music is pleasant sound.