graduations at the beginning of the band

What is the meaning of the two opposites graduations at the beginning of the band : decibels ? See screenshot.
Start of the band.jpg

You can make it be decibels with the drop-down menu system to the left of the track. The default is percent (100%=1.0). The sound meters are more obviously in dB.

I like editing in percent because almost all of the desirable content is in the loudest 25dB of the show which works out to be almost everything you can see in the % scale.

Yes, it does fall apart when you get down beyond about -25dB, but it could be argued your show is a basket case lower than that anyway. If you can only see your show on the sound meters, you have way more serious problems than picking the display standards.

Some people like to edit in dB, both blue waves and sound meters.


What is the meaning of the two opposites graduations

FYI - They are “opposite” because sound waves (air pressure waves) go positive and negative relative to the normal-average level… The microphone diaphragm moves in-and-out when sound hits it, and the speaker moves in-and-out when it reproduces sound.

decibels ? See screenshot.

Decibels are a relative measure. With digital audio zero dB is the “digital maximum” so your dB values are normally negative. Technically, the dB values in Audacity are in dBFS, which means decibels full scale. 0 dBFS is the maximum value you can get with a digital-to-analog converter or an analog-to-digital converter and it’s the maximum value that a regular (integer) WAV file can hold. Audacity uses floating-point so it can go over 0dB internally/temporarily.

The loudness of sound in the air is measured in dB SPL (sound pressure level). In this case, 0dB is the quietest sound that can be heard (by a person with normal hearing) and dB SPL levels are positive.

Thanks all of you, for your detailed explanations !