Do you mean the sound's volume is low?
There are often several volume controls on the soundcard, and ALSA might provide software emulations. For example, old Sound Blaster 16 cards had both an attenuator and a pre-amp', which showed as separate volume controls.
Also, individual programs may occasionally have their own volume controls separate from ALSA. These effectively mute the sound before outputting it. Most programs just change the master volume level though.
I'm using Ubuntu rather than Mint, so the user interface may vary slightly.
There should be a volume applet on the panel somewhere (if not, you can right-click on an empty part of the panel to add one). If you right-click on the applet you should get an option like "open volume control". This will bring up a dialog with a drop-down for the various sound devices (physical and virtual) on the computer, and show you the various volume controls for each, in a tabbed pane. Some options may be hidden behind the Preferences button. Sometimes more than one volume control may have an effect.
Hope that helps,
—Robert J Lee