Our amplified speakers do not produce noise, if you hear noise then the noise is coming from your bike and into the system. The tricky part is findout out where exactly, it is entering the system. Sometmes this can be multiple locations, but it is faily simple to locate the most siginificant source by following the below guideline.
99.9% of all noise enters through the ground, so a weak or bad ground can cause a humming noise. You will need to check ground on the amplifier, and if the problem continues, you may need to move the ground to a different point on the bike. Take a wire and jump the negative battery terminal on the bike to the ground on the amplifier. If you get louder volume in doing so, then you will need to get a better ground for the system. 99% of all noise enters through the ground, so if you have noise, always start with the ground, try moving it around on the bike.
Noise can also enter your system, through the audio input cable. Engine static can enter this cable along it path, so try rerouting this cable to see if the nose goes away.
Spark Plugs can also cause noise, try switching out your plugs for some resistor spark plugs
If you are charging your device while you listen to it, you may get what is called a Ground Loop nosie, and will need to add a Ground Loop Isolator to your system. This would just need to hookup between the amplifier and your device. They can be purchased at Radio Shack, Walmart of any car audio shop, amazon. They are available as in-line and can either be hooked between the rca plugs, or the 3.5mm headphone plug depending on where you want to install it for your system .