Changed os x macbook reminder sound, how to solve?

Question

macOS

for a reason that is unclear to me, the standard ''reminders'' application has changed the sound of warnings (notifications), it has become not beautiful. for some reason, there is no nominal sound in the folder with sounds (it is the same as on iPhones, the chord is called), even if you change the warning sound from normal to another through the poppy settings, everything changes except for the reminder sound itself. I can't find a solution to this problem anywhere else. the problem appeared after finding the laptop in sleep mode connected to the tv via thunderbolt to hdmi, if that matters of course..
ps os x 10.11..