@Colin @Avon DeRussate I can hear that video, played on my laptop, up to about 10.5kHz, which it says is about 11 years older than me. My first thought, too, was that maybe the speakers weren't reproducing the sound properly, but a quick test with an ultrasound detector app on my phone (but which can be set to detect as low as 1 kHz) showed that it was playing it - and my phone recording it - perfectly well, with a nice clear straight diagonal line on the waterfall chart for the whole length of the video (after 1kHz). I remember when my ears tested good up to 16kHz many years ago. :(