What does dB Stand for?
The unit Bel is named after AG Bell, but it is rarely used. Decibel (or one-tenth of a bel) is the most commonly used unit. The decibel can be used both in absolute terms or as a change in value, depending on the circumstance. When used as an absolute value, the unit value expresses a ratio to a particular fixed reference value. The most commonly used reference value is “volt”, and the suffix “v” is added in this case (for instance, 30 dB)
Since decibel is represented on a logarithmic scale, it becomes extremely easy to quantify and represent large ratios and multiplied effects. The scale starts with 0 dB (as 100 = 1) and is supposed to notate the lowest audible sound. A sound of 10 dB is 10 times more powerful, while 20 dB is 1000 times more powerful, as a direct result of this logarithmic scale. If the scale was linear, a sound of 10 dB would be 10 times more powerful, while 20 dB would only be 20 times more powerful (and 0 dB would be total silence, and not the smallest audible sound!)
If the scale was linear, and not logarithmic, it would have been extremely difficult to represent large ratios. Just like scientific notations, a logarithmic scale would allow the easier representation of significantly huge changes to a quantity. It is easier to denote a change of a trillion levels high in intensity by mentioning 120 decibels. Also, multiplicative operations are significantly easier on a logarithmic scale, enabling easier calculations for acoustic engineers.
Use cases of dB
The decibel is used in a vast array of fields.
- Human perception of sound - the most common use case of dB is to measure the human perception of sound. There are two different scales to measure this, a linear scale as proposed by the Weber-Fechner Law, and the logarithmic scale of decibels. Decibels are considered more useful due to their logarithmic scale
- Acoustics - used as a unit of sound pressure level.
- Telephony and Audio - Used as a frequency weighted power for audio noise measurements.
- Electronics - Absolute measures like dBm (decibels pegged to Milliwatts) and DBU are used to express power and amplitude ratios
- Optics, Video, and digital imaging - The relative loss/gain of decibels are used to measure link losses in optical links, and interestingly, as a measure to describe light intensity ratios.
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