Confuse about the waveform dB

[ydj609198]

Hi,
The help manual said"If the display is changed to Waveform dB in the Audio Track Dropdown Menu, the scale shows dB values for positive signals only, ranging from maximum 0 dB to the minimum dB".
Pls check the pic below,you'll see peak in the waveform at the bottom,does that mean the sound is very quiet at these points?Obviouly it's not.

[steve]

"dB" is a ratio. It is not an "absolute" measure, but is a measure of something compared to another (compared to a reference), where the reference level is said to be "0 dB".

For "sound pressure level" ("SPL" is a measure of "acoustic sound level"), the most common reference level is 20 uPa (equivalent to 0.98 pW/m2 at 1 atmosphere and 25 °C) which is around the threshold of human hearing. Thus all audible sounds are greater than 0dB SPL.

For audio signals, the reference level is the maximum 'valid' signal (the vertical height of a track). This is called "dB with reference to full scale", or more commonly "dB FS". This is such a common convention for audio signals that the "FS" part is often not written, though strictly speaking it should be. As in your screenshot, "0 dB" (0 dB FS) is the maximum level, and all other 'valid' signals are less than 0 dB (negative dB values).

[ydj609198]

May I add "0" at this area (check the pic below),then it may help to understand?

[steve]

If you make the track taller (drag the bottom of the track down), then you will see more numbers on the vertical scale:

firsttrack000.png (14.72 KiB) Viewed 1495 times

Yes there should also be numbers in the lower half of the scale like this (below), but the code to do that is difficult and no-one yet has volunteered to do it.

Code: Select all

____________________
  0
-12
-24
-36
-48
-60 ---------------
-48
-36
-24
-12
__0_________________

[ydj609198]

Thanks! Steve ,you provide great help for me.