sound - Only HDMI audio since installing Nvidia card: onboard audio device has disappeared

I replaced my graphics card with an Nvidia GT620. However, when I rebooted with the new card, my onboard Intel audio device disappeared completely - does not even appear in lshw.

Now the only audio output is the HDMI audio on the Nvidia card, which is annoying as my monitor has speakers but no headphone jack.

How can I make the HDMI audio device go away, and get back my onboard audio?

Sound-related stanza in lshw:

       *-multimedia
            description: Audio device
            product: GF108 High Definition Audio Controller
            vendor: NVIDIA Corporation
            physical id: 0.1
            bus info: pci@0000:02:00.1
            version: a1
            width: 32 bits
            clock: 33MHz
            capabilities: pm msi pciexpress bus_master cap_list
            configuration: driver=snd_hda_intel latency=0
            resources: irq:60 memory:fccfc000-fccfffff

Output of "aplay -l":

**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 7: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 8: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 9: HDMI 0 [HDMI 0]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

Output of sudo lspci | grep Aud

02:00.1 Audio device: NVIDIA Corporation GF108 High Definition Audio Controller (rev a1)

The cause of the problem was that the Onboard Audio was set to "Auto" in the BIOS: meaning when the BIOS detected the HDMI audio controller, it disabled Onboard Audio.

Setting Onboard Audio to "On" caused the Onboard Audio controller to reappear in Ubuntu alongside the HDMI Audio.