Power cable touching speaker cable

My system didn’t quite sound right this afternoon - some sibilance and possibly a bit of higher frequency distortion from left speaker. I found that power cable to Nova was in direct contact with speaker cable so I moved it and things seemed to have settled. I was wondering whether , from forum members experience, how significant can this effect be and what the mechanism is? Many thanks

Many here will extol the virtues of keeping power and signal cabling as separated as possible (or crossing at right angles if you must).

To my mind, the mechanism is almost certainly the higher currents in the power cable electromagnetically inducing currents in the signal cables.