Full disclosure - I'm actually trying to do this on elementaryOS Luna (beta) but it is based on 12.04 and I have tried the same in 12.04 from liveUSB with the same results (aka no joy).
So I have a Dell Adamo 13 with Intel HDA sound card. The internal mic isn't working after install / liveUSB boot and no amount of fiddling with alsamixer in terminal or installing DKMS from .deb has fixed it.
From sudo lshw:
From cat /proc/asound/card0/codec* | grep Codec :
description: Audio device
product: 82801I (ICH9 Family) HD Audio Controller
vendor: Intel Corporation
physical id: 1b
bus info: pci@0000:00:1b.0
width: 64 bits
capabilities: pm msi pciexpress bus_master cap_list
configuration: driver=HDA Intel latency=0
resources: irq:46 memory:f8600000-f8603fff
Any help appreciated. Ubuntu & elementary IRCs came up blank.
Codec: IDT 92HD73C1X5
Codec: Intel Cantiga HDMI