Sometimes when the sound volume is adjusted at a too high level with no file is being played, a noise would come from the speaker.

Try the following to avoid this noise:

Lower the sound volume of the computer

• If there is speaker icon shown on the task bar of Windows, right click this icon and lower the volume to a proper level. (This icon is usually located on the button right corner of the screen.) 
  
  
   
  
• Alternatively, click “Start”-->"Control Panel”-->" Sounds and Audio Devices” and lower the volume to a proper level at the pop up window.
  
  

Lower the sound volume of media player applications (such as Windows Media Player)

• Use the slider bar (or corresponding buttons of your media player application) to lower the volume to a proper level.

Lower the sound volume of the Philips speaker 

• If your Philips speaker set is equipped with a volume control knob, turn the knob to lower the sound volume to a proper level.