macOS High Sierra 10.13.6 empty trash sound playing repeatedly
If you are able to perform all your other tasks normally just like before and no longer hear the trash sound, you should be fine and there should be nothing to worry about.

Do test that the other audio is playing fine. You can also attempt to create a temporary file/folder, move it to trash and empty it to ensure that the sound plays only once.

Since restarting your computer has fixed the issue, it was most likely due to some bug in macOS High Sierra.

In cases like this, restarting is the first resort towards fixing.