There s a problem with the oscillation.
Dyson fan noise problem.
Try to clean the blower section of the fan.
This may be causing the motor to work extra hard resulting in the noise i have posted an article on how to do this at the following link.
Unplug your dyson personal purifying fan from the mains electricity supply before cleaning your machine.
Brush the outside of your machine with a soft brush to remove any debris from the shroud.
The airflow should be strong enough to lift a sheet of newspaper past 45 degrees.
Look for blockages in the air inlet holes on the shroud and the ball.
Get expert help troubleshooting from dyson to get the most out of your machine.