I don't think it's outrageous to claim average speakers can comfortably emit 20-20khz.
I don't think it's outrageous to claim that this is the comfortable range for most adults who experience some kind of hearing loss over time with age.
Children most definitely can hear above 20khz. I at least have the anecdotal experience ("most" here is keyword to argue against) that I experimented with testing ultrasonic frequencies on multiple devices to see if audio file formats made any discernible difference in range performance. This involved "swooping" a frequency starting at 20hz to as high as you can emit it (which usually starts to sputter in consistency around 18kHz.
I don't think it's outrageous to claim that this is the comfortable range for most adults who experience some kind of hearing loss over time with age.
Children most definitely can hear above 20khz. I at least have the anecdotal experience ("most" here is keyword to argue against) that I experimented with testing ultrasonic frequencies on multiple devices to see if audio file formats made any discernible difference in range performance. This involved "swooping" a frequency starting at 20hz to as high as you can emit it (which usually starts to sputter in consistency around 18kHz.