Where is the mono audio setting of vivo mobile phone?

When "Mono Audio" is turned on, the mobile phone will synthesize stereo sound into mono sound, which gives people a direct feeling that the sound has lost its original sense of space. If only one ear is wearing headphones, this function can be turned on. If you wear headphones in both ears, it is not recommended that you turn on this function.

Switch paths: Settings-Fast and Auxiliary-Barrier-Free-Mono Audio