Turn off the ringtone when you open the MacBook?

I have the problem that whenever I open my MacBook Pros (2017) a ringtone sounds and firstly I do not know why (because none of the programs that run in the background show a message) and secondly I try in vain in the settings this ringtone but you do not know where to do it.

Could someone help me with my problem? Is a little uncomfortable when I'm sitting in the Bib and my laptop then plays this loud ringtone and I interfere with others.

Then take a look here: https://tipps.computerbild.de/hardware/apple/wie-sie-den-mac-startton-ausschalten-326311.html

Have done as described in the instructions, even several times, but the sound is still there. Do not think that it is the starting sound of the Mac.

Did you also restart your Mac Book in between?

Yes, I have

Then I only know the following: https://praxistipps.chip.de/...halten_874

Otherwise, please search for yourself on the net or just ask directly at Apple