just a software that can loop your audio
http://www.cli-apps.org/content/show.php?content=88071INPUT 3 4 4000 OUTPUT
fade in = 3 seconds
fade out = 4 seconds
time parameter = 4000 seconds
if duration of input file > time parameter then cut your file at 4000 ssecond with fade in and fade out effect
if durration of input file < time parameter loop input file untill it gets 4000 sec and apply for every loop fade in and fade out effects then merge the files