Actually there is an ALSA device (libaudio to be more specific) mapped as arecord (and aplay) will work, but it seems that nothing else can use the DSP, and you have to ask it nicely (a DSP supported format, rate, etc.) which gstreamer does and generally won't with the default Flash parameters requested when my laptop is being used. It uses one of the plugin libraries to access the PCM stream via the DSP, so isn't as simple as /dev/dsp or /dev/audio.

Flash binds to libaudio, but I have no evidence it actually tries to access it.