If you are in and something / someone goes or is thrown out you say : "hinaus" or raus. If you are outside and sth/so is coming to me, you say "heraus" or raus. So 'geht heraus' is always wrong because heraus means TO YOU, geht means AWAY from you : a contradiction in se. "Raus" can be used for both cases. Especially if you ask someone to leave in a harsh, angry tone, you will use : "raus!" only. All three words always describe a movement from inside to the outside. The difference depends on where you /the speaker stands.
now we become more language scientific: I agree, that the Duden knows "herausgehen". Let me say the following to that: today "herausgehen" is most often used in slightly different way: aus sich herausgehen = to open up against other persons/to become more active in discussions / sports/ etc. or if something is pulled out somewhere: a plug / cone / etc. In Switzerland "herausgehen" will never be used in the sense of "leaving a room/a house resp. going from inside to the outside. In Germany and especially in Austria it's still used however it's a more "aged" form used to say the same as "herauskommen". For the daily use and for not confusing new-learners of German, I recommend my yesterday explanation because it's easy to memorize. hin-aus means away from me: HIN! her-aus means coming to me: HER! and it's following the most used practice in today's German speaking.
I'm a native speaker, so I don't have any problems at all. They sound completely different to me. If the difference in sound isn't of significance in your native language, it may be difficult to distinguish them. Just listen very carefully and try to make out the difference. And I recommend to use headphones. Listening comprehension is a skill that can be trained rather well. So, yes it surely will become easier for you.
I think they sound completely different but it's true that it's hard to tell the difference when you hear this computer generated voice speak. In real life you can easily distinguish the two. When you're not sure just click the turtle icon, then it will say it slowly and you can hear the difference.
@andrew.montanaro I get "ihr" because it sounds to me like "ear" "er" has a more "air" sound. And yes it gets easier. I may be at a lower level than you but I guess it took me longer to get here with all the retries. Edit just noticed BallsMcChin's post. It's good to know I'm on the right track.
See my detailed explanation before. In your case /question hinaus = raus, whereas hinaus is more distinguished language, raus more daily use /shortcut. "Er geht aus" means : he goes out to see his friends, to a party or the cinema etc. So the focus is not on "from inside to the outside" but to hangout or visit any events that are "outside". However you will use "ausgehen" even if you are already somewhere outside. For a girl/woman you would say: sie geht aus. A second meaning of 'sie geht aus' is e.g. a candle is near to extinguish. A third meaning is: some of your materials /food / usable are near to end, you will say : die Milch / das Toilettenpapier geht aus.
In this sentence, Ihr is the subject because it is the nominative second-person informal plural pronoun, like "You three! You are going out!" Note that it is only capitalized because it is at the beginning of the sentence.
Ihr/ihr can have many different meanings. In the dative case, it does mean her, but you (formal) would be Ihnen. Perhaps you were also thinking of the second-person formal possessive determiner, like in this sentence: "Ich habe Ihr Auto gefunden." Used in that way, Ihr translates to your and could be either singular or plural.