Decibels made simple in 5 minutes

We explain what decibels are and show how to calculate gains and losses without a calculator. You just need to remember a couple of values and you can easily work out the rest.
Decibels are used to compare power levels, but can be used to compare changing voltage levels at a set impedance.

[@louco2]

Nice trick, tank you so much for taking the time!!

[@richardlangner]

I'm pleased to have helped!

[@RealJomo]

Well done Richard.
Reminds me of being at college, using dB to define filter slopes. I can't do that now!

[@wormius51]

Very simply explained. It's only now I learn decibels are not a measurement unit of sound.

[@richardlangner]

Thanks for the comment. Yeah, decibels are just multiples of a certain power. It can be sound power, or radio power, etc.
Powers given in dBm are a multiple of 1 milli-watt. i.e. 3dBW will be 2 mW
Powers given in dBW are a multiple of 1 watt i.e. 3dBW will be 2 watts

[@flapjack9495]

Why do dBs double for voltage changes? I know watts = volts x amps, or I²R, but neither of those seem to explain it.

[@richardlangner]

For *voltage* dB you are correct that I²R applies. The number two in I²R represents x2 that doubles the dB for voltages.
Thanks for asking, it keeps me on my toes!

[@SDX9000]

Thank you, your video showed me a couple of new valuable perspectives on dBs! Only so far ALL videos about decibels continue to be misleading because their authors choose "the correct subject for decibel" - in this case "Power". At least you mentioned in the end that dBs for Voltage are quite different. But what if I come here to learn about dB SPL? Or perhaps more exotic dBFS or something even more rare - different explanations talk about one but not another, and then we want to learn how amplifier power relates to SPL... :)

[@richardlangner]

Decibels ALWAYS refer to power! SPL transducers output a voltage, and the video shows how to work out power from measuring this voltage.

[@SDX9000]

@@richardlangner I agree that dB SPL is comparable to dB Voltage, only it is not a all obvious for me or people who are looking for explanations of decibels.
If you say decibels are ALWAYS referring to power then are you implying that calculation with dB SPL or dB Voltage can not be done without recalculation into power? It is a nice lifehack, only not intuitive for someone who only uses dB in the context of SPL. :)

[@richardlangner]

Decibels are relative power. Remember that power is voltage V x V x I (voltage squared times current). To square a number using logs, you simply multiply by 2, hence we use 20 log instead of 10 log when working with voltage. If your setup doesn't change between measurements you can use voltage measurements and calibrate the SPL scale using 20 log. No need to recalculate power.
I'm glad to are interested enough to ask the question - I hope I have answered it.

[@SDX9000]

@@richardlangner According to this approach: sengpielaudio.com/calculator-db-data.htm are two types of quantities expressed in dB. So depending on perspective, dB is not always about power. But I certainly like your approach - I wrote down for myself your explanation that "dB value of Voltage multiplier is exactly 2x (double) the dB value of Power." - haven't seen it this clearly before.
I do have difficulty finding reference for "power = voltage squared times current" - this may be one more of the confusing parts about decibels, when in other contexts "P = U x I".

[@andrew_langner]

I may have actually learnt something tonight. let's see if I remember it in the morning.

[@rickyelvis3215]

where is the simple bit?

[@eternaldoorman5228]

🤣

[@MurugeshSurya-id4pt]

Thank you

[@richardlangner]

You're welcome