Now that I'm pushing 60 it's clear my relative perception of tones has shifted somewhat. Although I've had no reason to have my hearing formally tested, as someone involved in video and audio production (as well as being a long-time home theater enthusiast), I have enough digital media samples with which I'm intimately familiar I can tell the sound I'm hearing has shifted from what it once was.

I've been thinking about trying one of those mobile phone apps which give you a test of different frequencies and then provides and EQ preset to correct signals (as much as possible). This seems like a good idea and conceptually no different than the hardware I use to create screen profiles for displays and the calibrated microphone I use to adjust my home theater. However, I haven't done it yet because so far I've yet to find any tool that discloses much technical detail about it's doing and how. Being familiar with high-end audio DSP processing from the production side, I'd like visibility into what it's doing so I can assess how much theoretical support and/or rigor there is behind it. Would love any suggestions...