How do I know I'm listening safely?

How do I know I'm listening safely? What about tinnitus (ringing of the ears)?

Fidelity Custom Earphones were created by audiologically sound principles and may prevent noise induced hearing loss (tinnitus) by enhancing signal-to-noise ratios for the everyday, active user. Only the music is amplified, not the “noise”. The exceptional sound quality and comfortable fit are integral to our design.

It is still possible to experience tinnitus after using your Fidelity Custom Earphones due to listening at too high volume levels, but, it is much less likely due to the isolating characteristics. The added isolation will allow you to listen at more nominal levels and still hear the detail you need to perform at your best.