Re: Newbie RMS question

Martin Eisenberg wrote:
Randy Yates wrote:

First point: DECIBELS ALWAYS REPRESENT POWER RATIOS. This is
universally, eternally true. Memorize it now and you will
greatly simplify everything associated with decibels for the
rest of your life.

So the reason that is stated is that the label "fRMSasDecibels"
implies you're trying to express a voltage (which RMS implies)
as dB, and you can't - you can only express power, or a ratio of
powers, as dB.

What about the fact that a musical discrete-time sequence may well
not originate from any kind of physical system?

Then an assumed impedance must be stated.

Isn't dBFS defined in analogy but not with reference to the
relations of electronics?

I've never seen any decibel system not refer to a power ratio, if
that's what you're getting at. Perhaps I didn't understand your
question.

Martin, I acknowledge that most of the folks here (yourself included)
know about these various refererence systems (dBm, dBFS, dBA, etc.). I
am simply being a stickler on the units because, in this context, I
believe the original poster's problem was that he wasn't thinking of
the units correctly. I in fact identified a place where he was using
volts in a power calculation!

So, if I can summarize and cap this discussion, decibels (dB) are
defined to be a ratio of power levels, and using other units (e.g.,
volts) without an explicit method of expressing the resulting power
(e.g., by an assumed impedance) is meaningless, just as a
specification of "5 meters" is a meaningless indicator of speed.

--Randy

.

Relevant Pages

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