Normal Breathing 10dB...
Soft whisper (at 5m) 30dB...
Normal Conversation 60dB
Busy Traffic 70dB
Average Factory 80dB
Niagra Falls 90dB
..
Decibels are a logarithmic 'ratio' of relative power.
Strictly speaking it is incorrect to say dB.
Because the next question is decibels relative to what.
For example if a test tone is at a certain level and increases by about
3 decibels it will have twice the power of the original tone. But we
still won't know the actual power level of the original signal or the
new one.
It could be one micro watt increased by 3 dB to 2 micro watts.
Or one milli watt increased to two milli watts.
It could be 1000 watts and increase to 2000 watts.
All three are a 3 dB increase/relationship between two power levels.
Working mainly in telecoms for some 40 years, we usually had 'Reference
to one milli watt' or as our 'Zero dBm'. I recall we covered the math
about decibels in first or second year telecomms at Tech. College!
But there are others decibel (ratio) references.
Radio transmitter people for example may use used dBw 'Reference to one
watt'.
Also there were dBa (then mostly used as a noise reference level on
circuits). Zero dBa was IIRC equivalent to about minus 90 dBm, but was
frequency shaped to conventional voice telecommunication circuit
requirements.
Then audio people use 'Sound pressure level at a certain distance from
the centre of the cone of a loudspeaker'. a certain level being
considered, by them, as a zero reference.
Was happy to see one of the motoring magazines get it right; they
referred to noise levels within tested vehicles in dBa. Nice to know
somebody there with a good technical background knew what they were
referring to!
So decibels (With reference to Alexander Graham Bell, Scottish Canadian
immigrant, who invented the telephone) are one tenth of the logarithmic
ratio of two powers but are in themselves strictly meaningless.