Is it legal for the police to hide and enter a backyard w/o going to the front door due to a noise complaint?

I had a small party that received a noise complaint and the police came. They did not go to the front door, instead they entered the neighbors yards and surrounded us. They tried to hide and sneak up but failed miserably and were immediately spotted. We were not drinking yet the police entered the patio and looked around with flashlights despite my protest to go to the front door and talk to my dad since I am a minor. They told me to sit down and continued looking around. Then as they were leaving they my neighbors garage door open and looked in the garage, even going so far as to take one step in. I have alot of respect for police just not the ones in my township and I feel like their actions were unnecessary and illegal. Did they trespass by entering through backyards and stepping onto my property without going to the front door first or does the noise complaint allow them to act as they did?