Do you have an analog portable radio that you can hold near the suppressor and see if it causes noise? I can't see how it would. First, APC is a reputable brand. Secondly, there is probably very little in that device beyond MOVs, and MOVs should look like an open circuit until they get tripped. There should be no significant RF generation going on in there. The Furman PST-8 previously mentioned is definitely an upgrade over any APC, but I still can't see why any APC model should cause this problem. If anything, the series-mode protection (SMP) in the Furman actually increases the complexity of their circuit significantly over APC.
I'd check it with a radio, and I would try another surge protector you have lying around. I do think the radio would be a fair test to see if it generates RF because if the surge protector were sending RF over its outputs, it would also be broadcasting it electromagnetically and should be audible this way.
You can try checking a radio both in FM and AM; sometimes AM makes certain types of noise audible even if it's a fraction or multiple of the main frequency. Harmonics, etc.