Sound is all around us and can be measured to protect and inform us, as some sounds are not safe. In fact, loud noise can actually damage our hearing. So, the intensity of a sound is measured using decibel. As the human ear is incredibly sensitive, you can hear everything from your fingertip brushing lightly over your skin to a loud thunder clap. As far powe> is concerned, the sound of the thunderclap is approximately 1,000,000,000,000 times more powerful than the smallest audible sound. That makes a huge difference!
Formulas to calculate Decibel:
 When power is given:
The most basic form for decibel calculations as given below,
\(N_{dB}=10log_{10}(\frac{P2}{P1})\)
 When voltage and current are given:
\(N_{dB}=20log_{10}(\frac{V2}{V1})\)
\(N_{dB}=20log_{10}(\frac{I2}{I1})\)
Uses:

The decibel is mostly applied in
acoustics
as a unit of sound pressure level. In this, the reference pressure in air is set as the threshold value of perception of a human. There are many comparisons that are used to describe separate levels of pressure.

The decibel is used to express the ratios of power or amplitude in arithmetic ratios in electronics. The total gain of decibel can be easily calculated by adding up all the decibel gains.
Decibel Meter:
Sound can be measured with a device called as decibel meter. It measures and samples sound. Decibel meters are also known as soundlevel meters. It can even be accessed on a smartphone through apps. Measuring the sound of an environment with a common device like a smartphone that many people always carry may help protect their ears more often.
Decibel Scale:
On the decibel scale, 0 dB is the smallest audible sound. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. A noise level chart showing examples of sounds with dB levels ranging from 0 to 120 decibels.
Decibel  Sound  Source 
10 
Almost inaudible 
Normal Breathing 
20 
Audible 
Rustling Leaves, Mosquitoes 
30 
Very quiet 
Whisper 
40 
Quiet 
Stream, Refrigerator humming 
50 
Limited Sound 
Quiet office 
55 
Normal Sound 
Filtering coffeemaker 
60 
Fairly Quiet 
Normal conversation 
70 
Irritating 
Vacuum cleaner, Hairdryer 
75 
Constant Sound 
Dishwasher 
80 
Unpleasant 
City Traffic Noise 
85 
Loud 
Lawnmower 
90 
Extremely Unpleasant 
Violin 
95 
Noisy 
Farm Tractor 
100 
Extremely Unpleasant 
Train 
105 
Even Louder 
Large drum 
110 
Extremely Loud 
Symphony Orchestra 
120 
Extremely Loud 
Thunderclap, Boombox 
Continue learning more about Sound and Decibel with more interesting examples and diagrams @byju’s