Rallymania,
You normally won't hear No 1 being started as it is masked quite nicely by 2, 3 and 4 which are already running (if the starting seq is 4-3-2-1). All donks are started priot to takeoff, BTW.
The "windup" sound you hear airborne is the "airflow induced noise generated by the retraction of the wing flaps", as our FAs say on the PA. The reverse happens as the crew extend the flaps for landing.
It's THE trademark of the BAe 146/RJ. In addition to the fumes!
