Possible causes

1. The different sound is produced by the type of accessory you use.
2. The airflow in the vacuum cleaner can be (partly) blocked by an object stuck in the nozzle, tube or hose
3. The vacuum cleaner has a damaged motor.

Solutions

1. Check if the vacuum cleaner sounds normal again when you stop using the accessory you were using.
2. Make sure the hose, tube and nozzle are not blocked by an object

If the above solution(s) did not help to solve your problem, please contact Philips Consumer Care in your country: Contact Page