the meaning of -dB

[LfO]

Reading a few audio primers around the web, I find that decibels are basically a measure of amplitude of sound/loudness/volume. These seem to indicate that 0 dB is silence. However, in Cubasis, Cakewalk, Sound Forge, on this site etc, I am constantly running into negative decibel values. What does this mean? What does it mean to normalize to -.5 decibles?

 

[regebro]

dB is a relative measure. So 0 db just measn "the same level as". As what you may ask? Good question. The asnwer is: "That depends".

Next question, please!

 

[Ibrow]

What he said.

In your example of dB, what you'd be normalzing to is a "supposed" clip point. Once you go over 0 dB, the signal is going to clip. So, at "0 dB" in this case, it's the crossover point from loud to clipped.

 

[grinder]

Here's the simple explaination.

http://prorec.com/prorec/articles.nsf/files/EA68A9018C905AFB8625675400514576

And part 2.


http://prorec.com/prorec/articles.nsf/articles/3F50D03B51D16EF386256904007DFFC0

 

[LfO]

Thanks for the info - the article was particularly helpful.

Now I'm confused about the clipping issue, though. I was under the impression that clipping was a universally bad thing, so why do the recording programs allow you to increase levels into the clipping zone?

Thanks,
Derek

 

[TexRoadkill]

There are 3 issues.

1. In the real world 0db is silence and everything goes up from there.

2. In the analog electronics world 0db is the best quality signal (generally speaking) and can go way down or a little bit up. The amount that you can go above 0db and still have a good signal is usually referred to as 'headroom'. The amount that you can go down and still have an audible signal above the noise floor relates to the 'signal to noise ratio' or the 'dynamics range'.

3. In the digital audio world 0db is the loudest possible signal before clipping and you can only go down from there. The greater the Bit Depth the lower you can go (until you reach the limits of your analog to digital convertors signal to noise ratio).

I assume the reason they let you clip the audio in software is because if they put restrictions on it it would make many processes confusing and everyone would wonder why the hell it won't it let them turn the track up?!