Startup Sound (neither a chime or a series of beeps)

For some reason whenever I start up my computer, in the middle of the loading bar the screen would suddenly black out with a chime like sound and then suddenly the bar resumes and I arrive at the login screen. This doesn't happen when I turn on the computer in safe mode, and I suspect it might have something to do with the Respondus Lockdown Browser, which also forced my desktop into a blue background which I managed to fix, and I've also temporarily uninstalled the browser. But the sound is still there. I have also added my etrecheck report. Thanks!