CRJ Whistling...

[TedUnderwood]

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...

[transducer]

Also heard that noise many a time. Icing conditions in the cloud need to be present, no rain though, just cloud. There is a resonance on the airframe and the more dense the cloud the louder it gets, very loud sometimes, and almost immediately the ice detector gives an ice caution message. The ice detector uses a change in frequency on the tip of the probe to detect ice so is suppose that is also what is happening to the whole airframe?

[Clandestino]

Oh, it's Canadian cloud penetration detector. It's fitted to Q400 too but I'll be damned if I know what is whistling when you get her inside a cloud. I'd guess it's those long wipers' arms.

The ice detector uses a change in frequency on the tip of the probe to detect ice so is suppose that is also what is happening to the whole airframe? Not quite... the ice detector vibrates and as it gets iced, it gets heavier and vibrates slower - that's change in frequency that triggers icing alert, it has nothing to do with acoustics.