I don't know about the audicity settings, since I don't use it in fact. But fact is that the settings as described above is 44.1k for the samplefrequency and the bitrate at 16. Eventhough 22.05k can sometimes still sound acceptable, but you cut off higher frequencies a lot. A 44.1k will contain information upto 22 khz, while a 22 kHz samplerate will not go beyond 11 kHz frequencies. A stereomix will most likely exceed the 11kHz by far.

To give an indication: the old cassetete decks often recorded not much more than approx 15-16 kHz. Most (older) adults also won't go much beyond that... Which means that you would miss out a lot sampling at 22k. A 32kHz samplerate (16kHz response) might therefore be still the limit for acceptable quality.

I'll be back...