Decibels (or dBs) can be an intimidating unit system at first, but they are really pretty straightforward.
Decibels compare some value relative to a reference value
In other words, they are meaningless without a reference.
In our day to day lives, we know that 1 hour = 60 minutes, and 1 dollar = 100 cents.
But 1 dB needs a reference to understand it's value. It's like the potato chip bags that advertise "33% More!"
33 percent more?? 33 percent more than what!
As you can see, it all depends on what you are comparing it to.
Without wading into this dreadful mathematical bog (apologies to any fellow Mathletes out there), let's have a closer, practical look at these rascals.
You may also see them expressed as dBm or dBu. Units of dBm have the common reference of 1 milliwatt, while units of dBu have a reference of 0.775 volts.
0 dB means that the value is the same as the reference value... so 0 dBm = 1 milliwatt of power, just as 0 dBu = 0.775 volts.
This really isn't important our understanding, just don't think dBm or dBu are something completely different.
One great thing about these units is that they can be used to describe very big numbers.
10 dB = 10x boost
20 dB = 100x boost
30 dB = 1,000x boost
-10 dB = 1/10 reduction
A positive dB value indicates the signal is boosted while a negative number indicates the signal is reduced, cut, or attenuated.
A more useful way of thinking about it is that a 3 dB increase is double the reference value while a 3 dB decrease (shown as -3 dB or "3 dB down") is half the reference value.
The terms "attenuation" and "pad" are often heard when discussing microphones or mixing console inputs.
A device with a 10 dB attenuator (-10 dB) will reduce the input to one-tenth of the original value.
This can be useful in limiting how much signal makes it through and avoid saturating the input.
This is probably one of the most technical topics I discuss on the website, but these numbers get thrown around so much I thought I'd try to shed some light on these mysterious scoundrels.
If none of this made any sense - give me one more shot to explain it in context at the Gain Staging page.
Do not be intimidated by decibels.
They are here to help us produce music at just the right levels.