Still have nearly-perfect hearing, minus the really odd gap at 15kHz-16kHz
Not odd at all. Were you exposed to CRT TVs or old monitors for an extended amount of time? Their flybacks operated at one of several freqs: NTSC is 15,734 Hz, PAL is equal to 15,625 Hz, PAL M is equal to 15,750 Hz I wondered if TV/monitor technology was getting better over the years - the flyback scream got quieter and quieter as I got older. Turns out my ears were losing their sensitivity to it. I have a gigantic notch at those frequencies.