In Desktop/Web, visit User Settings (gear icon) under Notifications. Go to the section of sounds and select the Disable All Notification Sounds box. Below this option you can also tell individual sounds on or off such as message, user join or pings.
To keep Discord off your list of startup applications, you should turn off Open Discord in User Settings/Windows Settings/Mac Settings. It can also be turned off by using the start up space of Task Manager (Windows) or the start up items (Mac).
Toggle off "Message Sound" and "Incoming Call Sound".
You can also mute specific servers/channels by right-clicking them and selecting "Notification Settings."
Go to User Settings (cog icon) -> Notifications. Scroll down to the Sounds section. Here, you can turn off all notification sounds with a single toggle, or choose to disable individual event sounds like "Message," "User Join," or "Pings" to personalize your notifications.
To disable sounds on Discord, open User Settings → Notifications. Toggle off sounds for specific events like messages, calls, or mentions. You can also mute individual servers or channels by right-clicking them and selecting Mute. This helps reduce distractions while using Discord.