Hi Jess McBeath,
Welcome to Microsoft Office Community Forum. Thank you for sharing your concern with us today and we hope that all is well.
By the way have you tried to check if there are no pending updates inside Teams?
May I know also what type of license do you have?
For now I want to confirm if you have these options on your end?
You can get it when someone dials in via a conference bridge.
- Open Teams Admin Center
- Select Meetings > Conference Bridges
- Select Bridge Settings
- Make sure that Meeting entry and exit notifications are On

If someone signs in using web client or Teams client you will be able to see who it is signing in and if you want more control who is joining make sure that the Lobby function is activated for your meeting.
Or this one?
Meeting organizer can choose whether it should play sound once user joins or leaves a meeting.
If you will go to the Teams meeting in Outlook or Teams client and click on "meeting options":

Then you will have an option to disable this feature:

You can try these steps below on how to to turn off Teams sound:
Turn off Teams sounds
If you would like to disable sounds, the process is also straightforward:
- Open the Team Settings dialog, by hitting your Teams icon and then Manage Account.
- Hit Notifications.
- Then in the Appearance and sound section, turn off the Pay sound for notifications slider.

If you are using an older Team version, the dialog looks a bit different; so you’ll need to disable sounds a bit differently:
- In the Other section, set your notification sounds as shown below:

We look forward to your response. If you have other clarifications about this matter, you can get back to us by replying to this post.
Sincerely,
Sun Khou
Consumer M365 Forum Moderator
Microsoft Community