I bought this filter for hooking up my smartphone to my aux input in my car's stereo system. I was getting constant very bad noise when I listened to music on Pandora through my car system (I think the noise is from the processor in my phone). This filter took almost all of the noise away and I am able to enjoy my music. I do, still, however get these little high frequencies pitches of noise which aren't so bad and I can live with them.