Found Noise suppressor; now what?

Based on the picture and three leads it is a 12 volt "whine" filter. It helps reduce any electrical noise that may be present on the input supply to your radio, stereo, etc. Some may call it an alternator whine filter. It can help suppress ignition noise as well.

A ground loop isolator usually goes into the speaker lines and each speaker line would need one.

OK, thanks for replies. Mods that I'm doing is making more storage area and ran across this it. I'll leave it alone.

Thanks

Are the mods that you are doing to the sound system, is so you could try to leave it out and see if your speakers whine once the engine is started and then just reinstall it if they do, or like I said, it won't hurt anything if you still use it. I saw them in about half of the cars with big stereos when I was younger and into that sort of thing.

Usually a Band-Aid for a ground loop problem in the radio, but they usually work well. If it has a ground loop the speakers will hum and the sound will coincide with your engine rpm as the sound is usually caused by the alternator. It doesn't hurt to have it even if you don't have a problem so I would just leave it alone.

It filters out noises from your speakers. Humming and whining and such.