Decibel

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:

  1. When power is given:

The most basic form for decibel calculations as given below,

\(N_{dB}=10log_{10}(\frac{P2}{P1})\)

  1. When voltage and current are given:

\(N_{dB}=20log_{10}(\frac{V2}{V1})\)

\(N_{dB}=20log_{10}(\frac{I2}{I1})\)

Uses:

  1. 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.

  2. 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 sound-level 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:
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 coffee-maker

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



Practise This Question

An elevator car whose floor-to-ceiling distance is equal to 2.7 m starts ascending with constant acceleration 1.2 m/s2. 2s after the start, a bolt begins falling from the ceiling of the car. Find:
(a) the bolt's free fall time;
(b) the displacement and the distance covered by the bolt during the free fall in the reference frame fixed to the ground.