But, this reinforces that decibels do not implicitly measure any physical quantity, they only compare two values on a logarithmic scale. Of course, these comparisons are somewhat nonsensical, and you'd never hear them used in a real scenario. 'Bill Gates has 59dB more money than I do.'.'It takes Bob 3dB more time to run a mile than it takes Jill.'.'The distance from New York to Tokyo is 5.9dB more than the distance from Chicago to Los Angeles.'.

The following statements are perfectly valid: In contrast, decibels are simply a way of comparing two arbitrary values on a logarithmic scale.Įven though decibels are commonly used to measure sound levels, they can be used to compare any two values. Standard units of measurement (like meters, gallons, degrees Celsius, seconds) always measure physical quantities against a constant reference. The first thing to understand about decibels is that they are not units of measurement. It is almost never used, as the deci-bel (1/10 of a Bel, since 'deci' is the SI prefix meaning 'one-tenth') is far more convenient. The official unit is the Bel, which is an order of magnitude or a power of ten, a single unit in the logarithmic number system. The unit they invented was initially called the Transmission Unit (TU) but was quickly renamed to the decibel (dB), in honor of telecommunications pioneer Alexander Graham Bell. This decibel unit allowed engineers to eliminate the previously-required complex calculations, and instead use simple addition. To simplify these calculations, Bell Telephone Labs invented the decibel for describing the magnitude of power loss. Predicting and measuring the performance and efficiency of these long-distance transmission lines involved complex calculations, especially when summing the power loss over multiple segments of long-distance transmission cables. In the late 19th and early 20th centuries, telegraph and telephone lines were quickly circling the globe.

While decibels are most commonly thought of as describing sound volume, one might be surprised to learn that the origins of the decibel trace back to measuring electrical power loss over long-distance transmission cables.

Decibel scales