Opus at sample rate of 48khz, still only encodes frequencies up to 20khz of listening range (think of opus as having 40khz sampling rate). This is same as audi

Opus at sample rate of 48khz, still only encodes frequencies up to 20khz of listening range (think of opus as having 40khz sampling rate). This is same as audio CDs, which although are in 44khz sampling rate, have a red book recommendation to always filter out anything over 20khz. Thing is, most people can't hear well over 16khz. Some can hear 18khz. 20khz is peak possibility. To encode 20khz wave we need 40khz sampling rate. Everything else is marketing.