Definition
A unit used to express the ratio between two levels of power, voltage, or sound intensity on a logarithmic scale. One decibel equals one-tenth of a bel, and the scale is logarithmic so that each 10 dB increase represents a tenfold increase in power.
Plain English
A way of measuring how loud a sound is, or how strong a signal is, compared to a reference level. The numbers don't increase evenly — every 10-point jump means ten times more power.
Context Anchor
Seen in aircraft noise discussions, headset noise-reduction ratings, airport noise limits, and radio or avionics signal descriptions.
Derivation
From 'deci-' (Latin decimus, meaning one-tenth) and 'bel,' a unit named after Alexander Graham Bell. So a decibel is literally one-tenth of a bel. Knowing this helps explain why decibels, not bels, are the practical unit — the bel is too large for everyday measurement.
Why Pilots Care
Aircraft must meet strict decibel limits for certification, and pilots use the measure to choose proper hearing protection.
Grounding Statement
A cockpit can become tiring or damaging to hearing when the sound level is high, and decibels are the usual way that level is stated.
Intuition Check
A decibel is not a fixed amount like an inch or a pound. It compares levels on a multiplying scale, so a small change in decibels can represent a meaningful change in sound or signal strength.
Example Sentence 1
A typical piston-engine cockpit measures around 90 to 100 decibels, which is why active noise-reducing headsets are standard equipment.
Example Sentence 2
The airplane was certified to a maximum of 95 decibels at the measurement point.