Probably not the compressor for the reason you suggested SpyderAnn, but it could've been air RELEASING from the air bag via the release valve! That usually only lets air out when the load lessens Johnny, but if the bike went into the garage & shut-down with a bit of a load on it, then the pressure reduced as things got cold while it was garaged, once you started it again & the bag started warming up the pressure could've been gradually increasing as it warmed & prompted the occasional release of air.
My RT does that under similar conditions, so often that I worried a little & so spent quite some time searching for the leak. Did that every early morning ryde until I worked out that the air bag, being fairly close to the exhaust (& cat if still fitted) heated up & expanded fairly quickly, especially on those bright mornings following cool nights!! So if I parked it in the late arvo after some 2-up ryding, left it to cool down overnight, then still in the cool of the next morning, rolled it out to start up only to leave it sitting idling while the engine warmed up, I'd get those intermittent releases of warming air from the expanding air bag - much like many people do in the morning! :shocked: Anyhoo, I know what it is now, so I don't panic, but it can be a little entertaining for people not in the know if they are standing near while it 'psssts' at them every now & then! :roflblack:
Of course, YMMV, but for what it's worth, there's my 2 bob on it. :thumbup:
