The OnePlus 3 is one of the best values when it comes to flagship devices. It has a great build quality, great specs, and pretty great software. Even so the mod community is all about tweaking devices so you get the very most out of your purchase. Developer "abhi08638" has come up with a whole list of audio mods for the OnePlus 3.
Mono Surround activates the front earpiece speaker alongside the bottom speaker anytime speaker mode is on. This is kind of what has been done with Boom Sound 2.0 on the HTC 10. Mono Surround Sound plays all audio through one channel. This gives you 2 mono speakers the earpiece and bottom speakers. Camcorder Mic Gain increases microphone gain for audio recorded through the camcorder. This attempts to compensate for overly aggressive noise cancellation when the camcorder is recording. There are a few other audio mods as well. Head to the link below for full instructions. This does require root by the way.
via XDA