I received this product today. However, the Dyson AM07 produces a whistling (wind) noise even at low levels (certainly from level 3 of 10) that is much louder than the motor noise. It sounds like the wind whistling through the keyhole when the steam extractor is running. The noise comes from the nozzle, not from the engine. The pitch of the whistle changes constantly between two pitches (level 4). You can even hear the whistle in the next room or up the stairs. Is this normal? Does anyone have the same experience?