Here's what my Echometer provides. Saying the name spans the x-axis (time) from 50 milliseconds to 450 milliseconds. The bottom display covers the full range of hearing of a young person, from 0 to 20 kilohertz. Most of the world we hear is below 4 kHz. The upper display shows overall magnitude of the sound. There do seem to be quieter frequencies (2, 6 and 9 kHz). A good portion of the sound from 4 to 6 kHz continues after the word is said, suggesting significant background noise at these frequencies. The "L" sound seems to have components up to 13 kHz frequency. Maybe these are harder to hear for older folks. The "R" sound may include that ghostly 16 kHz spike - maybe also harder to hear. Still, I doubt it's that simple. If so, older people would be unable to understand speech.
This article is most interesting. The folks here say it depends on pitch:
One of the more interesting things to come out of the yanny/laurel debate was the discovery that, by changing the pitch of the recording, you could adjust what you heard. In general, people heard yanny more consistently when the pitch was lower and laurel when the pitch was higher.