I cant hear the dialogue

This also happens to me, he hears the dialogue but I do not.. I am using the friend pass version and my friend has the full version. We are playing on Origin/PC. Is there any more information I can provide?

@SerGoulding Can you check your sound settings and ensure that it is outputting correctly, eg if you have a stereo set up that it is not outputting in 5.1. 

I'm not sure what you mean. The game is outputting sound just fine through headphones and the game has all sounds (e.g. the plane propeller at the start, the crowds cheering etc). The problem is that none of the characters speak their voice lines. This applies to the main characters and NPC's, but not to say one of the police officers who yells "get off the bus!". They fully animate and so on, just no voice audio. This happens to just me (the free guest) and not my paid for friend who can hear the dialogue.

I notice that, like OP, I was playing Vincent. So maybe this matters?

@SerGoulding So there are different audio formats, mono, stereo, surround and a dozen others. If for example you are listening back on a stereo headset or speakers and the sound is outputting in 5.1 then you may be losing out on 3 channels of audio. In both the game and on your device you will have options to change the sound output, can you ensure that the game and your computer are outputting in stereo and then try again.

Let me know how you get on. 

Okay I got it to work. Had to google 5.1 etc.. I was indeed on 5.1 while my friend had stereo. For anyone who might find this useful I found the option to change this in Sound > Playback > Speakers (the device I use) > right click "configure speakers" > change to stereo. Not sure about in game settings but 'headphones' works.. 

Thanks for the help!

@SerGoulding Glad to hear that it is working, enjoy the game.