Is there a certain distance above which it may affect the sound?A generally applicable threshold can't be defined, because many system dependent variables are involved. IMO, though, 10 feet is unlikely to be a problem in most systems.
Relevant variables include the output impedance of the component driving the cable; the capacitance per unit length of the particular cable; whether the interface is balanced (xlr) or unbalanced (rca); the susceptibility of the particular components to ground loop issues (particularly for unbalanced interconnections); the resistance of the shield or other return conductor in the cable (particularly for unbalanced interconnections); the rfi/emi environment; and the synergy or lack thereof between the sonic effects of the cable and the overall sonic character of the system.
Regards,
-- Al