I don't really have a clue. I just think the way it works is so weird and it's even weird that science still is mostly clueless.
Everytime I spike i also get a sense of "feedback" (I don't know if that's the right word, I googled it. A word that has to do with microphones and speakers and stuff), in my head. It's not dizziness but a strange sensation as if the sound is circulating in my head very fast. (hard to explain).
Spikes, I guess, are either psychological or they're temporary damage to wherever the damage occurs. Or a combination of both.
There's at least one other possibility, I think: that the spike is neither psychological nor [always] physical damage.
Let me explain:
Neurons are like the wires in your home, literally: right down to the rubber insulation that protects them from dissipating energy, or touching other wires (in the brain, the insulation is made of myelin instead of rubber). In the home, when the rubber insulation is damaged, it increases energy leakage, and increases the likelihood of two wires touching. Same with the brain: often times, when neuronal transmission fails, it's because of damage to the myelin, which leads to current 'leakage', or to neuronal 'cross-talk'.
Back to the home example: when the light switch is off, and the electrical current is still, there is no leakage or cross talk. And when the switch is turned on, leakage and cross-talk will occur. But we wouldn't say we're necessarily causing further *damage* to the switch each time we turn it on. Rather, we can simply predict that whenever the light switch is turned on, leakage and cross-talk will be the symptom.
The same could be going on in our heads: spikes could simply be an indication that a degraded neuron is being used. Not damaged - just used. Of course, it's almost impossible to [currently] know if that's true or not, and no doubt some things do in fact cause more damage - so in this case I actually agree with
@Bill Bauer that caution is likely the better play. But situations like yours, where a perfectly safe 70db noise has led to a spike - I wonder if it's just because something about that sound frequency activated your damaged circuits, got them all hot and bothered. If I decide to become a tinnitus researcher, this is something I'm very interested in figuring out - whether spikes actually mean we're hurting ourselves, or if it just means that we're already hurt.