Rommel gave you the basic spill on analog freq usages but also remember that many AD/DA chip mfgs choose slightly different specs.
Much of the old equipment used less than 3.5K bandwidth and thus the T-1’s could use 56K channels and have some out-of-band signaling, supervisory, and error detection taking place on the diff between 56K-64K (8k left over per channel). Much of the old analog transmission systems also clipped drastically when doing OOS-QC’s 3Khz. They used many non-linear devices and their QC’s tolerated big db losses on the fringes. These losses were desired for analog multiplexing and called guard bands.
Back to what is the standard now…, You posted it. Much of the mic and speaker final end devices don’t have a good freq. response past your posted values. They were good enough for Sprint’s “pin drop” commercial campaign in the ’80s, though.
Dwayne