It's like what
@MattK said: Yes, you had an audiometry exam and it showed no hearing loss. But my guess is they tested to 8000 hz, the normal level for most of these tests. That is because that is toward the upper range of what humans normally hear. But there are more advanced tests that go beyond that level -- so they can see how your ears respond to sound that is higher than what you normally would detect.
When I had my first hearing test done, I also was told everything was normal. But when I went for a full audiology workup, in advance of doing sound therapy, they found I did indeed have hearing loss, way up high... about 14,000 hz (I keep forgetting the exact number). My loss is mild in one year, moderate in the other. Yet I never feel like I can't hear, because these frequencies are not in the range I normally perceive.
You will hear many folks on this board say they have tinnitus with no hearing loss, and I basically consider myself one of them. But in many cases, we just have a loss at a very high frequency.
The above advice
@Johno gave was good: Always wear ear protection in loud environments, try supplements for protection as well (I personally go with NAC and magnesium).