[xjsb125]

Reaper is a free tool that has some filter and EQ options that may help alter the sound of the track. Other non-freeware options include Sound Forge and Audition. Is your source a compressed audio source like .mp3, .aac, or .mp4? If so it may hurt your overall quality once you complete your work, by compressing the audio data yet again. Noteworthy that there is not a program out there that will just have a magic filter to "clean up" a track and make it sound better. It requires a lot of different options that all work together to achieve a sound you are looking for. Make sure you create a backup copy of your original file in case you change the sound in a way you don't like. After you do some work on the track, take a break. Come back the next day and listen again and make sure it still sounds the way you want it to. Lots to consider, but there always is in the world of audio. Hope that helps you!