The first symptom of a problem with aspirin is gastritis soon after taking the pill. It presents as a very real "burning" feeling exactly where the stomach is...in the middle, just under the ribcage. It is most pronounced as faster acting on an empty stomach where it might almost be considered normal. Taking it with food should avert the problem completely.
If you get the burn even WITH food then it is a pretty good sign that aspirin isn't for you. The smaller the dose, probably the lesser the symptoms.
Gastritis is different from heartburn, which is not common with aspirin.
Aspirin ccauses tinnitus in most people...it just does. I ignore it because I have some degree of tinnitus all the time and become aware of it only if I read the word TINNITUS!