I've come to the sad realisation that my 40-year old ears no longer have their original upper frequency response.
It is not a severe problem. Treble above 12KHZ is of very little of interest anyway in music.
If you are suffering much lower down in the midrange then you must see a doctor. Use this to check to see if your hearing loudness curve is "normal" - it should look like the typical equal loudness contour - if it does not then see a doctor.
Don't be surprised if you can't hear the 16 KHz tone - most people over 40 can't.