Dave Plowman wrote in message ...

Indeed. And with 'voltage' dBs, which will be the type used for quoting
the loudness of appliances etc, 6dB is a doubling of the actual voltage
measured. 3dB is a doubling of power, so applies to amplifiers, etc.

Just in case any confusion has been introduced by talking about
"types" of dBs, there is no such thing as a "voltage dB" or a "power
dB". A dB is a dB, i.e. a specific ratio, which by definition is
measured in power, but which can also be measured in voltage (or in
current come to that) as long as the two measurements share a common
impedance.

CRB