Unfair Lease Violation Notice

I need some advice.  I moved into my apartment a couple years ago.  I am on the second story.  The first tennant my complex had below me would yell at me for walking in my apartment because he could hear my footsteps due to the floor structure being so poor.  He even threw dog feces and a dirty diaper on my balcony and threw fireworks at my sisters car.  I reported him to our leasing office and they did nothing but he eventually moved out.  But then they moved another bully below me.  He verbally assaulted me for walking in my apartment because he can hear every sound.  I work late nights and come home and go to sleep late.  I fall asleep watching TV on my computer but it has never been loud enough to hear outside the apartment and I am pretty sure that it falls within the city ordinance for noise levels.  I don’t think I currently own anything that loud.  I reported the neighbor downstairs to the office for harrassment.  Several times he has voiced noise complaints against me with no proof and I wasn’t being loud at all. 

One night he called at between 1am-2am to report loud music blaring from my apartment and a peace officer showed up and reported back to the leasing office that he didn’t hear any noise from my apartment at all.  I had been watching a movie but I had to have the subtitles on because I could barely hear it.  Everytime this man has made a complaint, there was nothing to complain about.  I am not in violation of my lease, nor am I in violation of the city ordinance in terms of sound.

Today I came home to an official lease violation hanging from my door from the leasing office stating: "Per the lease contract and city ordinance, quiet hours are between 10pm-8am.  There have been reports of loud tv’s and loud walking at all hours of the night.  Please be considerate of the other residents around you and keep the noise level down."

I haven’t been making noise.

What do I do?

I am thankful for any advice.  I feel like I am being harassed. 

Thanks.

Tanya