The speakers themselves do not produce any noise at first. This is at least true for passive sound converters that depend on a feed player. And it is precisely there, i.e. at the A/V receiver or amplifier, that the cause of the noise is usually to be found. This is because amplifiers always emit a background or inherent noise. It is usually audible when nothing but the speakers are connected to the receiver or amplifier and the volume is turned down.
Defective or not This is how you test at home
Change the position of the speakers (e.g. exchange the left speaker with the right one at the amplifier output) and check whether the disturbing noise "wanders".
If the position of the noise source remains unchanged, there is much to suggest that the source of the fault is in the amplifier electronics. If the noise hikes, on the other hand, you have an indication that something is actually wrong with one of the sound transducers.
More information on this topic can be found in the Teufel blog