If you are using ALSA, amixer can be helpful for your script programming.
When dropping the
amixer --help command in a terminal you will see something like this:
Depending on your soundcard, levels may be different than mine, but you can use
alsamixer in the terminal in order to check which levels and which features in your sound card you can call in a command to set the volume as you wish.
In my example, with my principal sound card (I have 2: the embedded and a PCI audio card), levels are from 0 to 100, this way I can change the volume of a desired input/output in my soundcard by dropping in a terminal the next command:
amixer -c 0 set Front 50DB
amixer -c 0 set Front 64DB
In the first command, the result will set the Front panel output to 78% level and the second one will set the Front panel output to 100% level.
In order to gather information related to your mixer controls, drop the
amixer command with no parameters and you will get a list. Or indicate which audio device you wish to see a list of controls with
amixer -c X (where "X" is the number of your audio device).
BTW: Remember that DB values are calculated logarithmically and not linearly.