The PlayStation2 emulator PCSX2 uses your computer's sound card when you play games. If you need to adjust the volume, use the Windows controls. However, because the game you want to play was designed to use the PS2 sound card, some games have other sound problems when you play them with PCSX2. You can configure the settings in the "Plugins" menu to find a setting that works for the game you want to play.
Click the "Config" menu, and select "Plugin/BIOS Selector."
Click "Plugins" to see a list of default plugins. "SPU2" is the sound plugin.
Click "Configure" on the "SPU2" line. Set the sound options how you want. You can configure a delay if the sound does not match the game's video, which is a common problem. You can also configure sound modules, effects, reverberation and more. The exact settings to use depend on the game you want to play. Experiment to find the best options for you.
You can also install different sound plugins with different options, if you want.