Dynamic range is the ratio of the largest signal a system can process to the noise floor of that system.
If the system has variable gain, though, then you could interpret this two ways:
- Fixed gain case: Dynamic range = (biggest signal at some gain x / noise floor at same gain x)
- Variable gain case: Dynamic range = (biggest signal at minimum gain / noise floor at maximum gain)
I'd generally assume definition 1 for an electronic circuit, where you're picking the best gain to minimize noise while maximizing signal and then measuring both at the same gain. However, when people say the human ear has a dynamic range of 140 dB, they're using definition 2, since the human ear has variable gain. Likewise for human eye.
When measuring mic preamps or ADCs with variable gain stages, I could use either definition.
- If the term "dynamic range" really only applies to one of these cases, is there a name for the other thing?
- If the term "dynamic range" can ambiguously refer to both cases, are there unambiguous terms for each case?
Example using the term "SNR":
Human Ear Range (Instantaneous) 85
Human Ear range (Total) 120
Definitions of dynamic range based on filtering out a -60 dB tone imply that the gain is fixed:
The EIAJ standard measurement for dynamic range is done by reading THD+N at an input amplitude of –60dB ... inverting the polarity of the THD+N reading, and adding 60dB.