Originally Posted by
43Inches
They probably felt the feathering props and assumed it was the flaps travelling...again expecting a certain feel, rather than crosschecking indicators (not the PFs job until the checklist). When you take flap you expect a little nose up and speed to reduce, which is probably what happened, and at that point what the PF was expecting and wanting to occur. It wasn't until; later when she realized power lever movement was not resulting in increased IAS that they started to comment on it.
As for differences in noise, the gates and clicks of the flap vs CL movement should be identifiable if the recording is clear enough.
The noise of feathering is very distinctive on the ground. One would think it might be similar in the air.
I can't remember how much or little sound is made by movement of these levers. Perhaps a current ATR pilot can let us know. We shouldn't assume that it makes a sound audible above the sound of the engines.