the SetDefaultAudioDevice() method takes a string argument deviceName, which is the name of the audio device to set as the default. The MMDeviceEnumerator is used to enumerate the available audio endpoints on the machine, and the foreach loop iterates over the MMDevice instances that correspond to the active render endpoints. The FriendlyName property of each MMDevice instance is checked to see if it contains the specified device name. If a match is found, the IMMDevice interface is obtained from the AudioEndpointVolume property of the MMDevice instance, and the default audio endpoint is set using the SetDefaultEndpoint() method of the IMMEndpoint interface.

The resulting output is a message indicating that the default audio device has been changed successfully. Note that changing the default audio device programmatically may require administrator privileges or other system permissions, and that you should use caution and appropriate security measures when working with system-level functions. Also note that this code depends on the NAudio library, which can be installed via NuGet.