s track.
In other systems, the impedances vary. You can compensate for this with the R1/R2 correction factor, but more commonly engineers just choose to work exclusively with either voltage or power to avoid any problems. Now, a purist could argue that decibels are defined strictly in terms of power (that’s true) and that all decibel calculations must be done with that in mind. I might agree except that I’ve seen engineers work strictly in terms of voltage and 20log(V2/V1), without a problem. They get the benefits of working in decibels without having to adjust for impedance, but they have to be careful not to mix in power calculations. It is a good example of how engineers use mathematically-impure methods that have practical value.
We’ve just touched on a few decibel concepts, emphasizing the potential problem with dB calculations using voltage. Back in 2008, EDN published a series on decibels that was an excerpt from Sound System Engineering, by Don Davis and Eugene Patronis (see Refs. 6 through 8).
Next time, we’ll take a look at how decibels are used to refer to absolute values. For example, a common power reference is 1 mW, resulting in dBm (decibels relative to 1 mW).