How can i stop the high pitch noise in my Dyson 24 vacuum?

I would say it is sucking air in and whistling.Take it to bits again and reassemble it carefully and make sure all the bits CLICK together well.You haven't put it together properly!Sorry.

rich
May 2015

The vacuum's airflow is restricted in some way - the motor has no air to move - the motor runs off-load and turns much faster and makes a higher pitched sound.

You can check for this by blocking where the air enters - there will be little change in sound.

After your work cleaning the filters something has gone wrong with the reassembly - air is not passing through as it should.

Good luck...
May 2015