Trigger PTT on Baofeng UV-5R with Arduino
You cannot "send an audio file" as a stream of digital data.

You can transmit the audio from the file as an analog signal.

To do that, you will have to playback the audio file and convert it to an analog signal.  

The bitrate doesn't much matter.  What matters (somewhat) is the audio bandwidth of the file.  In its simplest form "bandwidth" is the highest frequency present in the audio during playback.

Two-way radios like your Baofeng have a very "narrow" audio bandwidth.  They only pass frequencies between 300 and 3000 hertz.  That's about like a standard land line telephone.  Music sounds really crummy through it.  No bass, no treble.  Just mid-range.

You will need to play back the audio.  That's probably not something you'll do with your Arduino - it's too slow and doesn't have enough memory (or flash storage) to hold a useful amount of audio. It also doesn't have a real analog output.  What the Arduino software calls "analog out" is in truth a pulse train (see PWM.)  If you trasmit that, it'll sound like somebody chopping up a speaker with a chainsaw.

You'll want a small record/playback module that you can trigger with your Arduino to playback your audio, and a relay module to activate the PTT.

You'll need to reduce the signal from the playback module with a couple of resistors.  The microphone input of your Baofeng expects some few tens of millivolts, and typical audio signals from a playback module can be a couple of volts.  Just using the audio straight to the microphone input will result in terribly distorted (extremely crappy sounding) audio.



I've intentionally not posted any details.  Your project is a long way from a point where there are details to be had.