I know this sounds routine, but sometimes it helps to review the normal methods. First, ensure you have an established routine you do at bedtime. The time needs to be consistent and the activity level the hour immediately before bed moderate to minimal. Do your best to get him down within 15-30 minutes of a "set" bedtime each and every night.
Second, do what you can to discourage the behavior. Talk about not getting out of bed before putting him to bed. We have a 2 1/2 year old boy who knows not to get out of bed until we come get him. Reward him for staying in bed until you come get him.
Third, change the environment. If he sleeps with no noise now, maybe try an air purifier or fan to give him noise. If he is used to having noise, try quieting the room a bit.
If all else fails, talk to the doc. They may be able to help you by looking at other "negative" sleep habits he may have.