I am sorry if I am not posting this in the right place. I am a 27 years old guy and I have a very bad ear at hearing high frequencies, I only figure out this today after doing more than 20 hearing tests (diff websites, videos, apps ect..) The result is I couldn't hear anything above 8khz on all these tests with regular average volume. Eventually what I did is, generating a pure sine wave then play it in whole human audio spectrum (20hz--20khz) I tried this with both headphones/earphones and speakers. if I turn up the volume 100% the highest frequency I can hear is 13khz, I could hear absolutely nothing after 13khz. I don't have any hearing problem or any difficulty hearing quiet noises (except these high frequencies) and I am also a musician and I have a good relative pitch, I can sing any note perfectly in tune if you give me a reference note and I am able to recognize any melodic/harmonic interval with no effort. Also there's one thing I didn't understand, there was one videos on youtube I tried, it was a sine-wave raising the pitch gradually from 20hz to 20khz, on this video I stopped hearing at 13khz on 100% volume but at 15Khz I started hearing again (something that sounded much lower than what the frequency must be, I would say) the sound is like a tape drop effect or like when you do a drop with the guitar whammy bar, which is very weird espeially that the audio is only a sine-wave which means there's only one harmonic which is the fundamental, so I converted this youtube video and played it on my DAW and opened a detailed graph to visualize what is happening. I saw nothing except a normal sinewave increasing the pitch! still hearing this weird thing after 13khz! is this normal ? Do I have some hearing problems ?