Проверьте с помощью следующего кода
using (AudioManager am= (AudioManager)WebViewActivity.Instance.GetSystemService(Context.AudioService))
{
int maxVol = am.GetStreamMaxVolume(Stream.Music);
float myVol= maxVol * volume;
am.SetStreamVolume(Stream.Music, (int)(myVol), 0);
using (SoundPool soundPool = new SoundPool(1, Stream.Music, 0))
{
int soundFileId = soundPool.Load(soundFilePath, 1);
soundPool.LoadComplete += (sender, eventArgs) =>
{
using (SoundPool soundPoolLoaded = sender as SoundPool)
{
soundPoolLoaded.Play(soundFileId, myVol,
myVol, 0, 0, 1.0f);
}
};
}
}