nice but not quiet

I (also in the office - without air-conditioning for the environment) due to the ongoing heat I ordered this promising device - Saturday ordered - Tuesday already there - so super fast! until then, very satisfied.

Appearance: power is a very good first impression, as seen in the video at Parl.

Function:
Connected to USB without problems and started. What my ears heard on stage one: a Pfeiffton I otherwise only know of smoke detectors where the Batterei is empty. So shrill and unpleasant. Of this I also read here in the reviews and hoped that it is not so bad - but it's not bearable when you have to concentrate!

At Level 2, I had hope and had quickly reverted - the Pfeiffton was quieter, but still audible: - / - also at level 2 is not "well-being" and concentrate quiet. At Level 3, the whistle was gone then, but also the fan was loud and unpleasant. The airflow rate was great at level 3 of 1-1.5 meters, but in the office I sit closer ... who wants to storm between the documents?

The function "air purifier" I have therefore not as well tested as the fan had priority for me. I'll send back the unit tomorrow to Pearl and was very pleased with their service and speed! At Pearl I would like to order again, just not this fan.

CONCLUSION:
So do not buy recommendation from my side!