My AC recently (I think, it's pretty new, possible I just didn't notice before) started making a whooshing noise. It sounds kind of like a sudden gust of wind, but it repeats every few seconds. Another way I can think of to describe it: imagine a PC cooler running relatively silent, but still being able to hear it. Now imagine it increasing its RPM noticeably for just around a second. Now imagine it doing this continuously.
It's a Whirlpool split type 12k BTU.
It also doesn't result in air being blown faster but, when you can hear it, if you stand in front of the indoor unit, air stops coming out for like half a second on just one side of the unit. Like the unit "chokes".
Things I've noticed and done:
efficiency doesn't seem to be affected, it still cools very well, but the sound is annoying.
it only seems to happen on higher temperatures. For example at 24 and 25 C. Any lower and my unit will start blowing out more air as well, which seems to result in a steady stream of air uninterrupted by whooshings.
if I lift the front panel, revealing the filters, the phenomenon stops! I thought something might be pushing on the filters, or that it's not closing properly, but I can't see any issues...
also, if I remove remove the filter on the offending side, it doesn't happen even with the front panel closed.
it doesn't always happen. Sometimes I run it for hours with no annoying sound, other times it starts a few minutes after turning on the AC. Sometimes it stops for a while.
Any ideas? I tried recording the sound but my phone doesn't really allow you to notice it when it occurs. I can try again if you think a recording would help.