18 month old not talking..

So my 18 month old isn’t talking. When he falls or cries he says “mum mum” but that’s about it. He used to say “hi” but he gave that up and won’t say it anymore. He went to his doctors appointment today, and his pediatrician put in a referral to audiology and for speech.. he said normally he wouldn’t be to worried, that the only part that makes him more less want to do put in the referral is because of the fact he used to say something and now he stoped saying it. So he is scheduled for his appointment tomorrow afternoon with the audiologist. Does any one else’s 18 month old not speak yet. My son does babble and he tries to talk little but we just can understand what he is saying at all. He can however point, he will go get something if you ask him, but he does get to where sometimes you have to call him over and over and over to get him to pay attention. I feel he’s fine but curious how your little ones are. Thanks for your help!!