- The definition of a decibel is a degree of loudness, or is a unit used to measure how powerful or loud a sound or signal is using a logarithmic formula.
When you turn your iPod up as loud as it can possibly go, this is an example of when you listen to your music at the highest decibel.

## decibel

noun

- Acoustics a numerical expression of the relative loudness of a sound: the difference in decibels between two sounds is ten times the common logarithm of the ratio of their power levels
- Electronics, Radio a numerical expression of the relative differences in power levels of electrical signals equal to ten times the common logarithm of the ratio of the two signal powers Sometimes an absolute reference is used in the power ratio (10 watt per sq cm in acoustics, one milliwatt in electronics and radio)

Origin of decibel

deci- + bel## decibel

noun

*Abbr.*

**dB**

Origin of decibel

**deci–**+

**bel**.

**decibel**

range of human hearing in decibels

## decibel

## decibel - Computer Definition

See dB.

A unit of measurement of the loudness or strength of a signal. One deciBel is considered the smallest difference in sound level that the human ear can discern. Created in the early days of telephony as a way to measure cable and equipment performance and named after Alexander Graham Bell, deciBels (dBs) are a relative measurement derived from two signal levels: a reference input level and an observed output level. A deciBel is the logarithm of the ratio of the two levels. One Bel is when the output signal is 10x that of the input, and one deciBel is 1/10th of a Bel.
A whisper is about 20 dB. A normal conversation is typically from 60 to 70 dB, and a noisy factory from 90 to 100 dB. Loud thunder is approximately 110 dB, and 120 dB borders on the threshold of pain. See dBm.
**INCREASE IN POWER LEVELS (WATTS)**
**Formula is dB=10*log(P1/P2)**
**DeciBels Output Signal Strength**
3dB 2x
6dB 4x
10dB (1 Bel) 10x
20dB 100x
30dB 1,000x
40db 10,000x
**ATTENUATION OF AMPLITUDE (VOLTS or AMPS)**
**Formula is dB=20*log(A1/A2)**
**DeciBels Output Signal Strength**
-3dB 0.707x
-6dB 0.5x
-10dB 0.316x
-20dB 0.1x
-30dB 0.032x
-40db 0.010x