Decibels (dB) - What are they and how to use them.
When working in any type of signal engineering it’s not long before you encounter the term decibel (dB) to show the ratio between two powers, or other quantities such as voltage, current, field strength, sound pressure, etc.
The decibel was devised by Bell Systems in the US to measure signal power in telephone networks. It is a very useful measure because it is based on a logarithmic scale, and therefore has the ability to show small changes within a very large range. Human hearing and vision have a near logarithmic response to strength and intensity, so decibels also relate well to human perceptions of light and sound.
The decibel is used in a very wide variety of electronics, communications, and sound engineering applications, as it is a very convenient way to describe a change in value such as the gain of an amplifier, the sensitivity of a loudspeaker, the loss through an attenuator, the shape factor of a filter, the efficiency of an antenna, the signal to noise ratio or the noise factor of a receiver, or anywhere a comparative logarithmic scale is appropriate.
Decibels can have either a positive or a negative sign, such as –dB or +dB. Click below to download the full decibel article.