I have been having sound problems with the speakers on an HP Ultrabook running Windows 8. Occasionally the laptop speakers stop working. When this occurs, I go to Control Panel>Sound, select the speakers(only one set to select), select Configure and Test. After selecting Test, I receive the message Device In Use. The device is being used by another application. Please close any devices that are playing audio to this device and then try again. I've gone to Properties for the speakers, Advanced tab and unchecked option "Allow applications to take exclusive control of this device". I've also used Run sndvol to try to determine the application, but it only shows Device:Speakers/HP and Applications:System Sounds.
The only way I've been able to get the speakers to work is to reboot or disable and enable the driver for the IDT High Definition Audio CODEC. Does anyone know of a way to determine the application causing the problem? Thanks in advance for your help.