To me This dosent sound like the problem of speakers.
Just switch on the receiver and increase the volume. This is basically the noise floor of the electronics within. For avr's like Yam, this should have minimal to no noise.
First check connections like what Audio_Freek mentioned, speaker conneections and power connections.
If this dosent fix it, then while it is on, just try moving cables (power and speaker) slowly to see if distortion increases or decreases. (Be careful not to make the wires loose and have it shorted). If this dosent fix then try moving speakers away from all other gadgets (again u dont want the wires to short, switch of and then move em). Then try the same with receiver, and then the speaker cable, try moving it away from other gadgets and power cables.
If this dosent fix it, then try switchin off all electronic equipment at home.
If this dosent fix it...is your receiver rated as 220V or, 110V connected to 110-to-220 converter.