Why after turning off all the accessibility services the sound is disabled and immediately after enabling accessibility of any third party app or inbuilt app ,this sound is enabled. I (perhaps everyone , I tested 3 phones at my home ) am facing this issue since two year. This is not an OS issue as it occurred in Marshmallow, Noughat as well as in Oreo.
I have found only one solution on the internet reagarding this & it is "Turn on Accessibility fpe at least one app"