I agree with others who suggested that you probably should have complained before checking out and asked for a refund then.
Of all the nights we've spent in hotels, we've been lucky and only had one really bad stay. It was at the Radisson in Orlando.
We were only staying one night and when we checked in we noticed that the lobby was packed with teenagers.
Around 8:30 that evening we started to hear a commotion outside and I went to the balcony and saw dozens of kids setting up musical instruments in the parking lot. By the time they were done there was close to a 100 piece marching band plus flag and baton twirlers. They then proceeded to practice at full volume for the next hour and a half.
It was like half time at the Super Bowl.
I still remember the reply I got from the man at the front desk when I called down to complain about the noise, which was overpowering even with the windows closed. I asked them to put a stop to it and the guy's reply to me was "But Sir, they have a competition tomorrow". If not for the fact that the noise woke up my 8 month old, I would have been amused by his candid reply. But I was amazed that the hotel was refusing to put an end to the practice and I couldn't speak to the hotel manager because she was gone for the day. I even asked the guy at the desk if he would put up with the noise if he was on vacation and he told me that you just have to put up with a certain amount of noise when you stay in a hotel.
I hunted around the room and found a number for the corporate office on a brochure and made a complaint that night. I even held the phone out the window so that the lady could hear the band. She got a good laugh out of that
In the morning I got to speak to the manager and she was very apologetic. I didn't even have to ask about comping the room... she just offered it after I told her about some of the answers I got from her hotel staff.