Question 1

How many decibels are in one bel?

Accepted Answer

One bel equals 10 dB. bels and decibels are logarithmic level units of the same quantity, so they convert by a constant factor. The formula is dB = log((1 × 3.162278^B) ÷ 1) ÷ log(1.122018).

Question 2

How do I convert bels to decibels?

Accepted Answer

Multiply the value in bels by 10. For example, 100 B = 1,000 dB.

Question 3

If it is a logarithmic scale, why is the bels-to-decibels factor constant?

Accepted Answer

Because bels and decibels both measure a level — the logarithm of the same dimensionless ratio. What is logarithmic is the dependence on that physical ratio (a fixed step in decibels multiplies the ratio instead of adding to it), but between the level units themselves the factor stays constant: 1 B = 10 dB.

Question 4

Where does the name "bel" come from?

Accepted Answer

The bel is named after Alexander Graham Bell and was the original unit for logarithmic signal loss at Bell Labs. In practice almost everyone uses its tenth part, the decibel (1 B = 10 dB), since it gives a more convenient numeric resolution.

Question 5

What does doubling power or amplitude mean in decibels?

Accepted Answer

A decibel is a ratio scale, not an absolute value. Doubling power (a ×2 ratio) equals an increase of 3.0103 dB (10×log10(2)); doubling amplitude (e.g. voltage or sound pressure) equals an increase of 6.0206 dB (20×log10(2)). Formula: dB = log((1 × 3.162278^B) ÷ 1) ÷ log(1.122018).

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