I think synaesthesia is the wrong interpretation of this phenomenon.
I hear flashes like that as a soft rush of blood around my eardrum. I'm pretty sure it's just the "acoustic reflex" (the muscles in my middle ear tightening in case there's a loud sound incoming). Obviously there isn't a loud noise here but like an involuntary blink, my body doesn't know that.
I hear flashes like that as a soft rush of blood around my eardrum. I'm pretty sure it's just the "acoustic reflex" (the muscles in my middle ear tightening in case there's a loud sound incoming). Obviously there isn't a loud noise here but like an involuntary blink, my body doesn't know that.
https://en.wikipedia.org/wiki/Acoustic_reflex