If you're using a Stealth 700 for PS4/PS4 Pro on a PS4 Slim using just the USB Connection (no Optical Connection), you can adjust the party chat volume level in the PS4 menu settings.
- Press and hold the PS Button to bring up the Quick Menu. Then, navigate to Party. (You can customize the setup of this sidebar, so depending on the setup that you're using, the location of the Party tab may vary.)
- Select Audio Adjust Mix. This will decrease/increase Party Chat volume. This cannot be used to completely mute Game or Chat audio; however, it will adjust the Party/Non-Party audio balance to a degree.
Certain games have controls for their channel; others do not. For example, Overwatch allows for control of the Chat volume within its menus.