What is dB (Decibel) and Why Do We Use It?

Decibel (dB) is a logarithmic unit used to measure the intensity of sound, power levels of electrical signals, and various other measurements. It provides a way to express ratios in a manageable format.

Why Use Decibel?

Logarithmic Scale: dB uses a logarithmic scale to handle a wide range of values. This is useful for measuring sound, where the intensity can vary greatly. For example, the difference between a whisper and a jet engine is huge, and a logarithmic scale makes it easier to understand.

Precision: It allows for precise measurement of small differences in signal strength, which is crucial in fields like telecommunications and acoustics.

Relative Measurement: dB measures ratios, making it easier to compare different levels. For instance, an increase of 3 dB means doubling the power, while a 10 dB increase represents a tenfold increase.

Practicality: The logarithmic nature simplifies calculations involving multiplication and division into addition and subtraction, respectively.

Examples

Sound Levels:

0 dB: Threshold of hearing

30 dB: Whisper

60 dB: Normal conversation

85 dB: Heavy traffic

100 dB: Concert

120 dB: Threshold of pain

Electrical Power:

0 dB: Reference power level (usually 1 milliwatt)

10 dB: Ten times the reference power

-10 dB: One-tenth of the reference power

Sound Levels (dB SPL - Sound Pressure Level)

20 dB: Rustling leaves or a quiet library.

50 dB: Moderate rainfall or a quiet office.

70 dB: Vacuum cleaner or busy street traffic.

90 dB: Lawnmower or loud music in a club.

110 dB: Rock concert or a chainsaw.

130 dB: Jet takeoff (at 100 meters distance) or a gunshot.

150 dB: Fireworks at close range or a fighter jet launching from an aircraft carrier.

Electrical Power Levels (dBm - Decibel-milliwatts)

0 dBm: 1 milliwatt (mW).

3 dBm: 2 mW.

6 dBm: 4 mW.

10 dBm: 10 mW.

20 dBm: 100 mW.

30 dBm: 1 watt (W).

40 dBm: 10 W.

RF (Radio Frequency) Signal Strength

-30 dBm: Strong signal (close to a Wi-Fi router).

-60 dBm: Good signal (in the same room as a Wi-Fi router).

-80 dBm: Weak signal (in a different room, farther from the Wi-Fi router).

-100 dBm: Very weak signal (on the edge of the Wi-Fi range).

Light Intensity (Optical Power)

0 dBm: Reference power (usually 1 milliwatt for optical signals).

-10 dBm: 0.1 milliwatt.

-20 dBm: 0.01 milliwatt.

-30 dBm: 0.001 milliwatt.