CRJ Whistling...
Not sure about other aircraft but in a CRJ, as the aircraft is flying through clouds at lower altitudes (I haven't really paid attention to the exact altitudes and/or speeds, venturing a guess, I'd say below F180 or so and upwards of 200 KIAS)...there is an audible whistle. You don't get this when flying thru rain, usually just when flying into clouds. Any ideas what causes this? I'm guessing it is something related to saturated air and friction going over the pitot tubes, tat probe etc...