+ dB to -dB increases volume

[Ringmaster]

I have reviewed "Audio - The Movie"; and I still can't logically figure out why a "-dB" results in higher volume. Maybe I overlooked this in the movie.

Could someone give me an "elementary" (not too technical) explanation?

[DJBohn]

Hi Ringmaster,
I have not seen "Audio - The Movie" nor I am not absolutely sure what you are asking, but I'll take a stab at it anyway. Volume range (or dynamics) in audio is always measured in -db, while the maximum volume on any recording (loudest sound without clipping of the wav.) will be 0 db. The volume range (largest -db figure) would be determined by how quiet the recording is (noise floor). That is the point where the music becomes hidden in the record surface noise, such as rumble or or hiss you will hear between 2 tracks. A cheap poorly done LP is going to have a smaller -db number than say a more expensive audiophile LP using better quality high grain vinyl. So a recording with a noise floor of -80 db will have a greater apparent volume than than a recording with a noise floor (or dynamics) of -60 db. I hope I explained it right & is what you were looking for.

[Craig Maier]

I am not sure what -dB is except that maybe it is referring to the fact that all dB numbers are referenced to 0 dB which is full scale output from the soundcard {in the digital audio world}. It is not possible to have a signal that is above full scale output which is 0 dB {for example, no signals can be recorded at full scale output + 6 dB in the digital world}. Anything attempting to be above 0 dB is just clipped by the system. That fact would make all dB numbers negative with respect to a 0 dB reference in a digital system.

This is different than in the olde analog days wherein 0 dB on your tape recorder was just some particular reference level. You could record at an average level that was - 10 dB referenced to that 0 dB reference level {having a bit more noise than recording at 0 dB} or you could record at + 3 dB above that level {having a bit more distortion than recording at 0 dB}.

So, reiterating - - - the loudest signal that can be recorded in the digital world will be at 0 dB on the Diamond Cut VU meters. Every other signal recorded is less loud than that. Something recorded at - 10 dB will be less loud than something recorded at - 3 dB, and so on. Silence with a 16 bit digital system occurs at - 96 dB.

I hope that clarifys it a bit.

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Here is some supplementary information on dB in the digital world:

A binary "Bit" produces a doubling of a signal.

A doubling of a signal is 6 dB {dB = 20 log 2/1}

So, an 8 bit audio system has a dynamic range of 8 x 6 dB = 48 dB

And, a 16 bit audio system has a dynamic range of 16 x 6 dB = 96 dB

And of course, a 24 bit audio system has a dynamic range of 144 dB

Even though the dynamic range of a digital system may be expressed as a positive number, remember that its range starts at 0 dB at its loudest point and becomes more negative going as the loudness decreases*. So, a 16 bit audio system is loudest at 0 dB and quiet {or muted} at - 96 dB.

*Note - Digital Audio Systems could have standardized on a different system of numbering. For example, it could have been set up that 0 dB could have been the quietest signal and +96 dB the loudest for 16 bit systems. So, the system that we have in which 0 dB is the loudest signal is just a matter on convention.

[Ringmaster]

I was just reviewing my Posts, looking for something else; and, I found that I had not responded to your threads.

I think what confused me is that my reel-to-reel tape recorders indicate that short bursts over 0 dB were acceptable; and, I thought it was even preferrable (maybe because of the Dolby Professional Noise Reduction). This is the method I used for pretty much all of my analog tape recordings; and playing them back, it sounds like I did not introduce any noise effects.

Your responses do clarify my confusion between analog and digital dB references. Some times, I still, momentarily, revert to the analog reflex; I guess old standards are difficult to erase.

I guess I just had memory over-load!

[Craig Maier]

Hi,

Analog tape decks still maintain some incremental gain above 0 dB on the VU meter. It is just that the system is somewhat less linear above 0 dB. That is not the case in the digital world since there is absolutely no incremental gain above 0 dB and thus only clipping (and clipping distortion) will occur when that happens.

Craig