Wirebook › Glossary › Decibel (dB)
What is a decibel (dB)?
In one sentence: A way of measuring how much stronger or weaker a signal is. Losing 3 dB halves it; losing 10 dB leaves a tenth.
A little more
Signals get weaker very quickly, so measuring them in ordinary numbers would mean writing lots of zeros. Decibels count in multiplying steps instead: every 3 dB is double or half, every 10 dB is ten times. Wi-Fi strength is usually given in dBm (decibels compared with one milliwatt), and it's almost always negative: −50 dBm is a great signal, −80 dBm is barely hanging on.
Walls are described by how many decibels they take away. A brick wall might cost around 9 to 14 dB, which leaves you a tenth or less of the signal.
It's a bit like… Like the volume steps on a speaker, where each click up feels about the same even though the power is multiplying.
See it in action
- 7Why does Wi-Fi get weaker through walls?Build a little house, drag the router around and watch the Wi-Fi signal spread room by room.7 min · interactive
- BonusWhy does the video call freeze when you walk to the kitchen?A phone holds one Wi-Fi box's baton at a time, and the phone decides when to pass it on.7 min · interactive