It is good his understanding is there.
You don't have to answer this to me but questions to ask:
Does he have a dummy? If so can you reduce it just for naps/bedtime.
Does he use a beaker/bottle - can you move to just a bottle or beaker at bedtime and use an open cup the rest of the time.
Had he had lots of ear infections or throat infections? Did he have any when younger? Are you confident on his hearing? Glue ear type thing?
When he is playing is the TV on? If so at times turn it off to encourage him to fill the noise and talk. Turn it on to watch then off for playing. Listening games and listening to music, stories also help.
You could try ten minutes a day describing his play with him, in an over the top way will help. Such as are you pushing the red car, you are pushing it fast, you are moving that car fast (car noises added in). Child's name is walking to the kitchen. Etc etc.
This helps the self-talk stage & helps Pre load them with words.
Also enjoy looking at noise books (the ones you press and they make a noise) so he can mimic them.
Also when asking him questions- leave time for him to reply, even if he doesn't then respond to his reply or what would be his reply (if that makes sense).
Also when he is in a good/well rested mood you can hold something slightly out of reach that he wants: drink/biscuit etc & encourage him to ask for it - when he attempts a sound (even though it does not sound like the object) reward him by giving it. You can get tougher on the release the clearer his sounds/words get. But high success at the start.
He is still young, so I would try this things at home for a while then at 2 phone HV for a 2 year check or to express concerns and you can say what you have tried already.