SNR vs DR: differences?

V

vogler

New member
could you tell me what is the exact difference bewtween SNR and dynamic range?
i found at least five definitions for DR:
  1. DR is relation between FS RMS signal to lowest discernable signal
  2. DR is headroom + SNR
  3. DR is relation between FS RMS signal to noise with -60 dB FS signal later filtered out
  4. DR is relation between FS signal to RMS noise level
  5. DR is relation between FS signal to peak noise level (or so, i'm totally lost)
and one for SNR:
  1. SNR is relation between FS RMS signal to RMS noise level

please provide me, if possible, formulas with indication where RMS measurements are taken.
/vogler
 
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In my limited understanding...

I think 4 is correct, for digital. Say, the number of dB above quantization noise. Depends on bit depth. For instance 16-bit is said to be 96dB.

Signal to noise ratio is related to the amount of headroom above the noise floor. The noise floor being related to the quantization noise as well as any other hash, hiss, and haze in the signal produced by the electronic circuitry or AC line noise.
 
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So according to Rane excellent page:
DR is ratio between FS peak signal level and RMS noise level, while
SNR is ratio between FS RMS nominal (usually +4 dBu) signal level and RMS noise level.
assuming that headroom is ratio between FS peak signal level and FS RMS nominal signal level it means that DR = headroom + SNR (option 2 and 4 from my question).
please confirm, there are to many web pages claiming different things.

two more nuances:
what regards "lowest discernable signal" - "discernable" means "not hidden beneath the noise floor on FFT analyzer" not "unhearable" as i've read that signals quieter than noise floor can be hearable to some extent.

i'm also adding nominal to the upper formula because AFAIK with really high headroom it's possible that FS RMS level could be higher than FS RMS nominal level (a few decibels but always). right?
 
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