Mastodon has a feature with which sounds play every time another user follows you, favorites one of your posts, boosts one of your posts, or mentions you in one of their posts. While some users enjoy this feature, it's apparent that others will not.
In order to disable these sounds, click on the right-most icon in the Notifications column header that looks like three horizontal lines stacked on top of one another. This will display a drop-down menu in which you can disable sounds for some, or all, of the mentioned conditions. In this menu, you can also decide what notification types show up in the Notifications column, and which types display desktop notifications. The trash can icon that is to the left of the settings icon in the Notifications column header will completely clear the notifications in the column.
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