Mid Sussex Neighbourhood Policing Inspector Darren Taylor said his team was first called out at 10.30pm after reports of a 'large rave' taking place in Janes Lane, Burgess Hill.
"Reports mentioned loud music and fireworks going off," the inspector said.
"Team located the source...it turned out to be a wedding reception taking place in the area."
Police were alerted to similar reports at 1am in Staplefield, Haywards Heath.
Inspector Taylor said: "A further report about a possible 'rave' this morning saw some of the team carrying out a search for the source of the music.
"Turned out to be a private party. Words of advice given to them about the noise and the time of day...music was turned off asap."
The incidents came on the same night as a 'large, unlicensed music event' in Steyning, which sparked a significant police response. Multiple road closures are in place and people are asked to avoid the area 'if possible'. Read more here