I actually want those suffixes mandatory, because there may be multiple plausible suffixes for each use. For example the loudness might be dB(A), dB(B), dB(C), dB(D) depending on the exact curve or even dB(SPL) if the sound pressure level is used as a proxy. So it is much more confusable than, say, "millis" when suffixes are implied.
This is right and all... But this usage still leads to confusion about what you are measuring your filter by.
There are filters we measure on power, there are filters we measure on signal amplitude, and "signal amplitude" can be ambiguous on some contexts too. There should be a way to specify this one better.
Well, dB is fully specified in that regard. It's always power. You can calculate the voltage gain from it under certain assumptions, and under normal assumptions you get that factor 2. But a -20dB attenuator will always reduce the power by a factor of 100.
