Could someone explain decibel levels?

[ScarletCyanide]

Okay, so I don't understand db's, logically 0db's should just be no sound... someone please fulfill my void of knowledge

[deadly_habit]

http://www.soundonsound.com/sos/1994_ar ... ibels.html

[safeandsound]

Decibels are named after Alexander Bell and the nomenclature is 'dB' not 'DB' 'Db' or anything else.

Decibels are a logarithmic unit and are always in comparison with a reference.

Examples:

0dB SPL is no sound at all.
0dBFS is a full scale digital signal relative to silence or theoretical bit resolution -96 or -144dB for example.
+4dBu is a value equal to 1.23Volts RMS

So it is not absolute and always a comparative value.

cheers

SafeandSound Mastering
music mastering

[AxeD]

The decibel scale is a reflection (of the logarithmic response) of the human ear to changes in sound intensity.
That's basically why you can hear 0dB. Read up on some theory and -if you want- mathematical theory and check your
knowledge with questions like:

Standing right near a pa tower at a DMZ night exposes your ears to a 120 dB sound level. An IPod produces 100 dB. How many IPods would be needed to produce the same intensity? (remember the dB scale is logarithmic)

The part that's confusing to me is with mixdowns, where you have stuff
hitting at -6 etc.. but it's still loud. Is that because the sound isn't actually traveling through air but just being
processed digitally / directly outputted or something?

(some of this might have been covered while I was writing the post )

[sburton84]

The part that's confusing to me is with mixdowns, where you have stuff
hitting at -6 etc.. but it's still loud. Is that because the sound isn't actually traveling through air but just being
processed digitally / directly outputted or something?

What you don't seem to understand is that there is no such thing as 'a decibel'. There are multiple different decibel scales used in various different contexts. As described by safeandsound above, db SPL is used for actual analogue sound waves (sound pressure); when you say an iPod produced '100 dB' you actually mean '100 db SPL'. When talking about digital signals however, you are talking about dBFS (decibels relative to full scale). With dBFS the maximum possible value is 0dB, anything above that gets clipped.

Comparisons of dB SPL to dBFS are completely meaningless; the only thing these scales have in common is that they are logarithmic. A digital signal of xdBFS can translate to absolutely any dB SPL level when played back depending on how loud the amplifier and speakers are turned up.

[deadly_habit]

that and there are different scales for your base db levels within your DAW or studio setting

[AxeD]

Yeah that dBFS part of safeandsound's post got my attention and I read up on it. Thanks for the explanation though!
Weird though, how they still use a kind of dB scale but it's not about sound pressure anymore. Guess I never knew this because
it's not that obvious in Reason (4).

[atticuh]

When in doubt, Sound On Sound.

[Triphosphate]

The part that's confusing to me is with mixdowns, where you have stuff
hitting at -6 etc.. but it's still loud. Is that because the sound isn't actually traveling through air but just being
processed digitally / directly outputted or something?

(some of this might have been covered while I was writing the post )

I think what you are describing is an effect of the Fletcher-Munson curve. In short, the human ear hears better at certain frequencies than others, which is why some things may sound equally loud even though the dB does not reflect it. For example sub bass (which is almost more felt than heard) and high hats.