it will be the relay, and it will be most noticable when on intermittant, as it will 'click' each time it opens.
When on 'full' wipe it only clicks when you first turn them on, power is then passing continuously through the relay as the wipers swipe back and fore
On intermittant, it's power on (click) = 1 swipe. power off. power on (click) = 1 swipe. power off...
Can't say I've noticed it in the civc, but had it in previous cars - I might just be tuning it out now
(though now you've mentioned it, no doubt I'll start to hear it again...
)