Could not load the clip provided however the most common cause(s) of this noise is,
1. Throttle tube elbow. Usually cracks and causes an air leak at the small tube to idle valve causing whistle noise on moderate throttle application at 2000rpm. This can be seen visually. (BMW 13 54 1 438 759 for 3.0 motor) or (BMW 13 54 1 435 627 for 2.5/2.8 motor).
2. Deflection pulley (at alternator). Bearing usually fails this noise is typically present from a cold start and may dissipate after a short period. (BMW 11 28 7 841 228).