Testing my ears?
larryhat at oregon.uoregon.edu
Mon Mar 6 09:43:32 EST 1995
In article <3j69j2$iur at agate.berkeley.edu>, beorn at swindle.Berkeley.EDU (Beorn Johnson) wrote:
>In article <larryhat-0203950903120001 at lhatmaker.uoregon.edu>,
>Larry Hatmaker <larryhat at oregon.uoregon.edu> wrote:
> [ ... ]
>- You'd probably have to find a very specialized tester, though, as most
>- of the Aud equipment is calibrated/ designed for the speech frequency
>- range (250 to 8000 Hz). Not sure anyone would have Hearing Level
>- calibrated outputs for ranges beyond that (HL is calibrated differently
>- than Sound Output Levels).
>After taking a hearing test a couple of years ago, and being
>unimpressed with the detail/testing method, I've wondered how
>hearing-test machines are calibrated. Ignoring for the moment the
>difference between Hearing Level (perceived?) and Sound Output Level
>(energy?), how can you calibrate automatically without having to worry
>about calibraing your calibrator (or can you? if not, how do you calibrate
>(and then, what _is_ the difference between Hearing Level and Sound Output
>Level, and how is that calibarted?)
Hearing level is calibrated on the principal of Just Noticeable Difference. If you were to test 1,000 normally hearing individuals who had never been exposed to loud noise, their ability to just barely hear/perceive a tone at specific levels would be noted as 0 dB Hearing Level. In other words, a tone with XXdB Sound Pressure Level (XX varying with frequency) would produce a just noticeable response as an average across 1,000 individuals.
There are generation/calibration units that one uses to make sure the Audiometer is producing the appropriate dB SPL in relation to specific International Standards Organization standards.
Hope that makes sense.
Center for Electronic Studying
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