What it means
Attenuation is the weakening of a radio signal as it passes through material. At 2.4 GHz, water and metal are the worst offenders, and a human body is mostly water.
In order of how badly they block: metal, water and bodies, dense masonry and concrete, then plasterboard and wood, then glass and air.
This is why a device inside a metal drawer or a full bag can be undetectable from two metres while the same device across an open room reads strongly.
It is also why holding your phone against your chest while searching is a mistake. Hold it out and low.
Related terms
The other pieces of Bluetooth vocabulary that change how you search.
- Unwanted tracking alert: How phones warn you
- Beacon: A device that only broadcasts
- RSSI: Received Signal Strength Indicator
- Advertising interval: How often a device broadcasts
- Bluetooth Classic: The older streaming mode
- Get warmer, get colder, Inside Scan
- An unknown Bluetooth device is showing up. What is it?, Identify
- Full glossary, the complete list
Common questions
Why is the signal strong but I cannot see the device?
Because it is inside or underneath something. Attenuation means a strong reading with nothing visible is a reliable clue to search the volume, not the surface.
Does Bluetooth go through walls?
Through plasterboard and wood, readily. Through concrete floors and metal, poorly, which is what makes floor-by-floor searching effective.
In the app: The scan shows this value live for every device around you. Read about Bluetooth Scanner.