I did the test on mosquitos ringtones test in front of my class in a psychoacoustical class oral expose (at the end of it, as an extra) when I was 19 years old.
We were in a new building and the acoustics of the room were top notch; the speaker system was also brand new and sounded good enough with music. I asked the people to raise their hands and to put it down when they would judge they weren't hearing anything anymore. Most of my classmates were girls, from 19 to 57 years old. I was the first to lower my hand and I felt very bad, viscerally insulted, on that very instant when I nervously giggled. Now I am 22 and the results are the same: I can only hear up to 17 kHz on normal listening volume. The 57 year old lady lowered her hand at 18 kHz, the big majority of the class at 20 kHz, there were four girl's hands remaining at 21 kHz, and only the very youngest of our class could hear the 22 kHz one, she was also 18 about to turn 19.
You guys need to consider something, the AVERAGE human hearing audition is 20 to 20k Hz for a NEWBORN. Anything above 20 kHz is considered above average and from the moment the newborn starts hearing the human voice, most importantly the voice of it's mother (which he can differentiate and prefer over the voice of three other women because he can recognize his mother's voice from how he heard it from the inside) the hair cells for the highest frequencies begins to rigidify and cease functionnality. We all loose those useless higher frequencies (only considered useful are the 250 to 4000 Hz for the conversation range (and those are the main frequencies used in music too), and only 125 to 8000 are measured in audiology), and at 18 years the same 20 kHz average has gone down to 12 kHz. All those numbers we see on YouTube and mosquito ringtones are inflated when we compare them to the scientifically proven audiological facts I just quoted you, those are from serious studies. Deafness is described in terms of acuteness of the loss on all of the freq. spectrum and how it impedes you to discriminate words. Average -90 dBHL from 125 to 8000 is severely acute and considered profound deafness (when external hearing aids (not a cochlear implant) can't help you), -75 is severe (you need some powerful hearing aids or an implant), -55 for your best ear is enough to get you free assistive listening devices (bed shaking alarm clock, phone transcripters, flashing light door ringer and fire detecter, etc.) from the Canadian government and this represents a bad case of presbyacusis, and finally, -25 dBHL is enough for free hearing aids and that is when you speak to your grand-father that often asks you to repeat and speak louder, it is part of the normal aging. Strictly speaking we never loose the frequencies near 12 kHz, we only need higher volume to hear them, as we do for all other frequencies as we age.
Those highest frequencies are of course the first one you loose when you work all your life in a noisy factory or something like that.
Why I think I was the worst performer of my class in my test was that I listened to music on my Sony minidisc player in the school bus for three full high-school years straight (from 12 to 14 years old), using the non-specially-isolating Sony MDR-E808 (without the foam pads) that came with the player, in a highly noisy environnement, and I did that one hour (2x30 minutes) a day, at 21/25 (while there was a volume safety lock option to block it at 22 maximum, level past which was considered dangerous I guess), while 10/25 plainly sufficed in calmer environnements. In those environnement 21/25 wasn't comfortable at all and it was fatiguing. And I was fatigued too when I came back from school during those years. Contrastively I always felt good during the two last high-school years where I didn't listen to music in the bus. It ruined my life forever.
J/k... I have one year of courses of an Audiology bachelor's degree followed at the University of Montréal (that I abandoned) now I pay the utmost attention and care for my hearing. I've gotten aware of the more dangerous situations when the air is acoustically polluted and satured, or when loud impact noise are being heard. I always carry plugs to counter those situations. I have lowered my casual listening volume in silence on my Creative Zen Vision: M from 13 to 10 and I feel like I can hear the music just as good. I think I have become more sensible for the frequencies that I had left and now I find concerts and discotheques environement highly discomfortable without plugs. What I do is I go at the bathrooms and put rolled up paper toilet sheets inside my ears, it does the job and I'm back to having fun; the next day all the friends that were with me at the event hear tinnitus-like ringing in silence and not me... I don't plan on hearing those ever again.
Edited by devouringone3 - 1/16/12 at 2:29am