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dB(decibel)
Understanding dB (decibel)
The unit ‘dB (decibel)’ is one you likely encounter often in various devices or matters related to acoustics. However, many do not fully grasp what dB precisely signifies and why it’s essential. In this post, we’ll delve into the basic concepts of dB, extending to real-life examples.
Definition: dB represents a unit of a physical quantity derived by taking the common logarithm of a ratio compared to a reference. The name of this unit originates from the inventor of the telephone, Alexander Graham Bell.
Why ‘Decibel’?
The ‘deci’ in dB stands for 1/10 of the value of B. In fact, 10 dB equals 1 B. The unit B itself is too large for practical use, so dB is typically employed.
Relative Unit
dB is a relative value. In itself, it holds no specific meaning. For instance, stating “A is 3dB larger than B” is accurate, but saying “A is 50dB” remains ambiguous. Often, when sound is described as “~~ dB,” it refers to the unit dBSPL, where the suffix SPL implies a specific absolute value.
Characteristics of the Log Scale
Being on a log scale, dB values are not directly proportional.
For units expressing power (e.g., electrical power), a change of 3dB indicates a doubling or halving of the power (=10log10).
In contrast, for units indicating amplitude (e.g., voltage), a change of 6dB signifies a doubling or halving of the amplitude (=20log10)
Power Ratios Corresponding to dB Values:
1:1 = 0dB
2:1 = 3dB
4:1 = 6dB
10:1 = 10dB
100:1 = 20dB
Amplitude Ratios Corresponding to dB Values:
1:1 = 0dB
√2:1 = 3dB
2:1 = 6dB
3:1 = 10dB
10:1 = 20dB
100:1 = 40dB
Units like dBSPL and dBm pertain to Power, while dBV, dBu, and dBFS relate to Amplitude.