This is a known issue with Dell laptops 7420/5420 Realtek audio driver updates and some Logitech headsets

With the headset connected, search for the Control Panel > Device Manager

Expand the Sound, video and game controllers to reveal the drivers.

Right-click on the Realtek Audio driver and uninstall the device.


Reboot and wait for Windows to reinstall the driver on its own.


Once installed, open Control Panel > Sound


On  the Playback select the default device then click Properties to turn off the audio enhancement options


Click Apply, then OK
On the Recording tab, select the default device, click Properties.

Click on the Advanced tab and uncheck the Enable audio enhancements option


Click Apply, then OK
Click OK on the Sound control panel window to close it.