We used to "make" louder headphones by taking two speakers, and using the floor as a third side, make a triangle to stick ones head inside and "crank it up".
I inadvertantly tested my hearing at home using a home written basic program to test my PC speaker. I wasn't using microphones to check the frequency rolloff of a PC speaker and thought that it cutoff a little early. As I was demonstrating this "fact" to one of my kids, he pointed out that he could easily hear the speaker at much higher frequencies than I could.
Well, it was good while it lasted. ;-)
My hearing is already pretty bad.
A little itty bitty drill that we use underground doesn't help. It puts out about 135 decibels.