> ATI Radeon HD 5470 Audio That should be the HDMI audio from the video card and as far as i know there is no support in OpenBSD for HDMI audio output. There lines from dmesg you need are:
azalia0 at pci0 dev 27 function 0 "Intel 3400 HD Audio" rev 0x06: apic 2 int 22 azalia0: codecs: Realtek/0x0887 audio0 at azalia0
