Hearing, digital sampling, etc
You may have heard of Meridian's Master Quality Audio (MQA) coding system to reduce the size of high-res files. A fellow named Hans Beekhuyzen has some videos on youtube that explain how we hear, why sampling rates matter, etc. There is good news for us old guys who are losing our high frequency hearing. It seems that it's not as scary a problem as it sounds.
See the link below for the part 1 video.
[url=https://www.youtube.com/watch?annotation_id=annotation_3806380967&feature=iv&src_vid=IxFafCO9khE&v=r_wxRGiBoJg]the Hans Beekhuyzen channel[/url