I\'ve got my computer(Windows 7) hooked up to the TV, and i very often change output device for sound between Digital Audio (S/PDIF)(High definition audio device) and my headset
I had a HDMI device that keeps changing it's name, so none of the existing solutions worked for me.
I eventually ended up with this powershell and use of the NirCmd app.
#File: TV.ps1
$name = "SMART*"
# list active audio playback devices. (Note for cature devices change Render to Capture)
$device = Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Render\*\" | where {$_."DeviceState" -eq 1} | foreach-object -Process {(Get-ItemPropertyValue -Path ($_.PSPath + "\Properties\") -Name "{a45c254e-df1c-4efd-8020-67d146a850e0},2")} | Where-Object {$_ -like $name}
C:\bin\NIRCMDC setdefaultsounddevice $device 1
C:\bin\NIRCMDC setdefaultsounddevice $device 2