MacBook Sound low Unless Sound is Open On System Settings

My MacBook has worked just find for more than a year. Suddenly no upgrades that I know of the sound is Leo. If I open sound in System settings it is normal again. But then you have the microphone on in yellow in the top part I forget what it is called (where File, Edit, View, Date, Wifi, etc.. are). It is unnerving & illogical. Why did this happen? I want the normal noise back without having to have sound open in system settings.