"Jan Philips" wrote in message
news
The understanding I want you to have is that a 96 KHz WAV file (say
of a tuba) will sound the same at 32KHz, 44 Khz and 96KHz, as long
as the extra high frequency extension afforded by the higher sample
rate doesn't have any audible consequences.
...
OTOH, a 96 KHz wave file will sound the same if properly downsampled
to 44.1 KHz because chopping off all information above 22 KHz
generally DOESN'T have audible consequences.

I'm wondering - why does DAT use a 68KHz sampling rate if it doesn't
do any good to go that high?

DAT uses 48 KHz and 44.1 Khz.

48 KHz was chosen to provide similar bandpass characteristics as 15 ips
analog tape. It was known at the time that 24 KHz was somewhat overkill, but
the difference between and 44.1 and 48 isn't really worth arguing about.