Thank you for your input, alot to think about.
Here is how I see it:
First of all, I understand the freq is on a log scale. If I were to color in the area under the curve with a pencil and measure it directly off the paper, y es you would not be taking into acount the logarithmic scale. However, I am not doing that, I am instead using the actual numbers so the scale the freq is plotted on is irrelevant.
The Db scale is logarithmic, but so is our hearing. Notice the graph does not plot it on a log scale. Again, direct numbers can be used if the ares is calculated using the numbers, not the actual area on the paper graph.
On the audiogram, it shows a o db at the top throughout the frequency range 0 to 8Khz. It is implied to me that a normal hearing person would have thiere scores plotted at the zero line. If that is the case, then a comparison can be made at each frequency, the normal person at 0 db and a hearing impaired person at whatever they have.
I dont know if the pure tone audiogragh takes into account equal loudness curves, I have the feeling that the two are related, but I dont know how yet.
Thank you for sending the link. To me, this is a LEGAL and not really a medical mesurement of hearing loss for the purposes of compensation, not for the purposes of measuring hearing loss.
I found the way they measured hearing handicap (HH) to be quite disturbing.
They first measure the thresholds of hearing at several frequencies, take those numbers and then average them. Thats fine that makes sense to me.
If your good ear measured 30 db average and your bad ear measured 40 db average then the overal weighted HH was calculated giving a 5 times weighted score to the good ear. Therefore the weighted HH was (5(30)+1(40))/6 = 31.67. Thats makes sense to me too. The 5 multiplycation is an emperical result probably determined thru research that takes into account the good ear compensating for the bad.
The disturbing parts - Initially they used only the frequencies of 0.5, 1 & 2 khz, finally later they added 3 khz. This makes absolutely no sense to me at all. In fact it actually seems to purposfuly ignore all the frequencies above 3 K, the very frequencies that get damaged by age and exposure to noise! The very same frequencies that carry most of the speech information! This formula does not even look at that at all! I wonder if the purpose of doing this is because they figure as people get older they lose hearing above th 3 khz so it would make it impossible to determine what hearing was lost due to exposure to noise on the job for example. Determing what hearing loss was done due to exposure to noise and what was lost due to the aging process seems impossible though. Maybe the low frequencies are more stable and are better able to measure hearing loss due to noise.
In any even though, this criteria does not measure hearing handicap or percentage hearing loss at all. It is a legal criterial used to determine hearing loss only in the very l low frequencies and is used as a tool for compenstion for hearing loss, not to give a picture of the hearing impaired persons hearing as compared to a normal persons hearing.
I did notice in thier formula HH capping out at 92 db. This makes sense in that 92 db minus the 25 db threshold they used is 67 db. If you have 1.5 % more loss for every db, then with a cap at 67 db you get 67 db *1.5% = “100”% loss. Many people can hear and function somewhat past 92 db, but you have to draw the profound line in somewhere. I think at 90 db for me, I can actually feel the speaker vibrating against my dead ear so thats the only reason I would get a score there.
I summary. The HH appears to be a legal criteria used for award compensation, not a complete medical measurement to get at least the magnitude of hearing loss accross the entire accepted frequency range of 0 to 8 K. I also still dont see where my calc’s might have had an error, although I am sure they are there.
PS - I wish they would test past 8 K. I know I hear as high as 16 K.