W0X0F,

Thanks for the informative thread. I fly so much it's good to get a different perspective on all those "why does that happen?" things.

One thing I hear exclusively (but only intermittently) on the ol' DC-9s is during engine start the FA announcements will be interrupted by a mechanical whoop whoop sound. It increases in pitch and frequency before dying off.

It sounds very much like some sort of EMI (like a charge/discharge) and clearly isn't a problem but I can't ever recall hearing it on any other a/c.

Also, are you flying DL126/DL127 any time soon? Headed out that way end of May.