Decibel scale and meters

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sgpatel

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I am confused about the decibel scale that is used on meters. I have been reading and trying to understand how meters work. I came up on a article where it was mentioned that 0db is the 'threshold of hearing' and then later in the same article it was mentioned that digital audio has a limit of 0db. This is what confuses me as to if 0db is the 'threshold of hearing' then how 0db be the maximum limit in digital audio. I apologize in advance for such a stupid question. Also the meter in wavelab and most meters display number like -48,-40,-32,-24,-16,-8, 0 db. Why are these negative if the threshold of hearing starts from 0db and upwards. :eek: . The article had the following chart:
0dB Threshold of hearing
20dB Quiet living room
50dB Average office
70dB Busy street
80dB Average factory
110dB Thunder
120dB Airport runway
133dB Threshold of pain

so then shouldnt the meters start from 0db,8db,16db etc....
Once again i do apologize since this might be very basic when it comes most board members.....any explanation would be helpful.....
 
I think the article might have meant that getting your levels past 0db digitally it is gonna clip which is bad for digital. Going past 0db in analog is fine most of the time though. I've been studying up on this stuff for a while now and can honestly say that I don't fully understand why leves start from - to 0.

edit to say as posted in another thread if 0db is the loudest you can go without clipping then everything else must be quieter. duh :o
 
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You need to differenciate between 0dBVU, 0dBFS and 0dB SPL... Uhhhh, I know confusing.
 
noisewreck said:
You need to differenciate between 0dBVU, 0dBFS and 0dB SPL... Uhhhh, I know confusing.
Click to expand...

I agree.

On digital meters, 0dB is the loudest signal that can be recorded.

But, that has little relevence to Sound Pressure Level (SPL).

To confuse the matter more, everybody has a different threshold of hearing. :D

For fun, you should look up the Fletcher and Munson Relative Loudness curves and get a good handle on them.
 
you have to understand that dB (decibel) is not a measurement. It is used to express the relative difference (or ratio) between two numbers...and one of those numbers being the letters that follow "dB". For example, in the digital world this is considered Full Scale....or 0. The decibel is a dimensionless unit and doesn't necessarily have to refer to audio.

Like with digital...you need to always specify what ratio you're talking about by adding letters after dB. dBSPL, dBFS, dbVU, dBu, dBm, etc. All of them are realitive to different numbers.

dBSPL=decibel Sound Pressure Level and references 20 micropascals (a pascal being pressure measured to one newton per square meter) which is the quietest sound a human can hear.

dBFS (digital world)= decibel Full Scale...Full Scale meaning 0.


and it just gets more and more confusing from there

:)


http://en.wikipedia.org/wiki/Decibel
ignore the math for now, that just shows you how it works scientifically and it'll probably confuse you for now....unless you're really good at calculus. :D
 
think of it this way...how else could we develop a standard for clipping or when a recording has reached it's maxium limit?
 
LeeRosario said:
think of it this way...how else could we develop a standard for clipping or when a recording has reached it's maxium limit?
Click to expand...

true...and not true. in the Digital world, yes. In the analog world, not necessarily. And in the SPL world...0 is the minimum not maximum like digital.

Forget about what the scale is and understand what the scale is relative to.
 
bennychico11 said:
true...and not true. in the Digital world, yes. In the analog world, not necessarily. And in the SPL world...0 is the minimum not maximum like digital.

Forget about what the scale is and understand what the scale is relative to.
Click to expand...


well I was talking digital, analog is something else, I know.
 
On the other hand....


a studio system that can reproduce 140db....WOW.


Probably a great horror movie for audio engineers. Call it, "Land of the Dead Ear Drums". (I'll be working on a better title)
 
A decibel is a unit of measurement.

It's one tenth of a Bel.

An inch is a unit of measurement.

"Dude, how can you have negative inches?"

Easy. You need a reference point. Once you decide where your reference point is, negative or positive just lets you know which side of the reference point you're on. If you install a telephone pole so that the top is six inches underground, you might want to say that it's -6" tall. The ground is your reference point, or zero in this case.

It doesn't change the length of the pole.

Thing is, inches are linear. Decibels are not linear.

Sound doubles every 6 dB. Length in inches does not double every 6 inches.

To measure sound using decibels, you need a reference point. SPL (sound pressure level) is a measurement of what we hear, be it produced by musical instruments, machinery, a tree falling in the forest or hippies. The scale is positive. Zero means no sound.

To record these sounds, we convert (arguably) natural acoustic sound waves into electricity. Electronic musical instruments and sound generation devices don't need the conversion. It's already electricity.

A number of people figured it would be convenient to measure the electricity relative to a different scale. So they shifted the reference point.

The thing is, all the different people that did this came up with their own scale. It doesn't change what a dB is, it just changes the location of the reference point.

Perhaps in terms of electronic devices, it's easier to refer to the maximum capabilities of the format rather than the threshold of becoming.

Now this would all be a lot easier with standards, but there are about 6 different ones.

To make things more complicated, if you ask several people, "relative to a specific scale, like dBFS, what is the standard operating level supposed to be?" you'll get answers ranging from -18 to -12 to -0.1 and beyond.

Or they'll ask you something like "peak or RMS?"


They'll clusterfuck you every time.



sl
 
snow lizard said:
To make things more complicated, if you ask several people, "relative to a specific scale, like dBFS, what is the standard operating level supposed to be?" you'll get answers ranging from -18 to -12 to -0.1 and beyond.

Or they'll ask you something like "peak or RMS?"


They'll clusterfuck you every time.



sl
Click to expand...


-20dBFS fer me
:D
 
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