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Comment on Audio cable measurements are driving me crazy — why don’t they null?!?

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marcos@lemmy.world ⁨22⁩ ⁨hours⁩ ago

So a signal of -40 dBFS is quite audible, since it’s all relative to 0 dBFS (full scale).

At -40, it doesn’t make any difference what kind of dB you are talking about.

(Well, if you are looking for superstrings evidence or even quantum gravity, it does, but I guess it’s not your case.)

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bigpEE@lemmy.world ⁨6⁩ ⁨hours⁩ ago
It sounds like you think -40dB is such a small factor it must be inaudible. It absolutely is, the ear has like 100dB of dynamic range

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Uebercomplicated@lemmy.ml ⁨22⁩ ⁨hours⁩ ago
en.wikipedia.org/wiki/DBFS

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- marcos@lemmy.world ⁨21⁩ ⁨hours⁩ ago
  Relevant line:
  
  US installations use +24 dBu for 0 dBFS
  
  That means the US definition you can’t hear anything below -24 dBFS. It’s the largest value there, it’s -18 for the EU.
  
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  - Uebercomplicated@lemmy.ml ⁨12⁩ ⁨hours⁩ ago
    BTW, you also seem to have misunderstood dBU. That is in voltage, which means the signal is amplified before you listen to it. I would highly recommend reading the wiki page on decibels: en.wikipedia.org/wiki/Decibel
    
    I think there’s good YouTube videos on how decibels and digital audio work as well.
    
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  - Uebercomplicated@lemmy.ml ⁨12⁩ ⁨hours⁩ ago
    What you quote is for conversion with analog levels, which is not what’s happening here. Everything I’m doing is 24 bit digital audio, which has 144 dB of dynamic range. That is a little over-kill, which is why most audio files are distributed as 16 bit, so 96 dB. That means you can hear anything from 0 dBFS to -96 dBFS (with proper dithering). That is why the cutoff point in the graphs I showed you is -100 dBFS, since you realistically won’t be able to hear below that anyway (audiophiles disagree), in the final file.
    
    -40 dBFS only represents how the signal is stored in the digital file. It has nothing to do with the signal’s actual volume. I play those -40 dbFS through my computer, then my DAC, which outputs at about 2 VRMS, into my pre-amp, which increases the voltage again, into my amp (which, again, increases the volume), and finally into my speakers, which output that -40 dBFS, which is now signal at about 70 dB SPL (actual volume).
    
    dBU is for analog line-level, and the conversion you showed is what I would use when routing my console back into my computer. But analog line levels are still very audible at -40 dBU, usually, not that that’s relevant.
    
    You have to understand that this is not real volume. It is just how the volume is stored digitally. If you have a -40 dBFS noise floor in your audio file, and the music has a 12 dB dynamic range peaking at -1 dBFS, you will hear the noise clearly throughout the entire track, because you are amplifying the entire thing greatly, since you are ultimately transforming this into dB SPL.
    
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