Hi!
The wires should not be tight as a bow string... on the contrary, quite slack actually, you should be able to press down easily if you press on the wire just a few centimeters from the servo arm.
No sound should be heard, not like a bow string. I hope you use the thinnest fishing wire available, that's what you should use on most 1-2m span airplanes, pylonracres, scale as well as F3A aerobatic airplanes.

Regards!
Jan K
Sweden