Can you guess this note? Perfect Pitch and Physics

Just thought I'd share my story of achieving an absolute pitch.

Before the age of 12, I had no desire to learn, perform or create music. But it was a time when I started hearing about DJs. So it quickly became a bit of an obsession with me and I started learning DJing as a way to perform music. Slowly but surely, playing other people's music became more boring with each day and I realized that it would be great to have your own music. And with that thought, I began my journey to becoming a sound-producer and engineer. 

Since creating a musical piece in a modern way often comes with a regular repetition, I couldn't help myself but notice that I could recall certain parts of the composition in my head. What made me wonder is that with this ability I could not only "listen back" but modify sounds in my mind the way they could be modified by different audio plugins and tools.

In a parallel to that, I also began experimenting with my voice. In other words, singing and beatboxing. One day I was strolling down the street, deep in conversation with a fellow musician. We were debating over a piece of music and at one moment I casually a passage without "tuning" myself. Then my friend wanted to repeat that passage with a smartphone keys app and when he played it with the original key he noticed that I actually sang it pitch perfectly. He asked me whether or not I have an absolute pitch. Naturally, I told him I don't have one.

But cases like that started to repeat and one day a friend tested me. I could always sing whatever note I was asked to sing but I was struggling to listen back and guess a note correctly. With singing, I felt like I've been recalling a pitch from the back of my mind and matching it with my voice, but with listening it was more of a like trying to find a pitch one semitone at a time.

A few years had passed and now in 99.9% of the cases, I can not only guess a note correctly, I can tell by how much is it off. I can also tell a difference between different A4 references and types of tuning. In general, it took me 9 years to develop such a skill, the only drawback being unable to enjoy the music without analysing it, guessing keys, etc., etc.