What does Unity use under the hood in Android/iOS?

I'm having issue synchronizing audio to gameplay on mobile devices because of the ridiculous latency in Unity's audio and seemingly no way other than asking user to manually adjust it.
I would like to know what Unity uses under the hood so I can go to the system directly and ask for relevant information. Does it use OpenSL ES, AudioTrack, or a mix of both depending on Android version/models/some other factors? What about iOS?
Thanks.