Hearing test on line?
Tinnitus, e.g. hearing a 'beep' need not correlate with the presence of a discontinuity ('dip') in the audiogram. On the other hand, noise-impaired hearing and presbycusis often cause tinnitus, especially when the slopes in the audiogram are very steep. (Bron: Audiologiebook)
With a simple audiometer you can check whether you have indeed “lost the treble”.