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AC & static pressure feeling
I agree with Jont that a feeling in AC is as when having static pressure in
external meatus, but:
>When you have pressure on your ears, there is lots of static (low
>pressure relative to high frequencies. He suggests that when you walk into
>the AC, the high frequencies are damped, but not so much for the lows.
>Thus the spectral balance is tilted heavily toward the low frequencies.
>It is, he argues, the strong low frequency bias towards the low end of
>the spectrum that gives the "pressure effect," just as in the case of
>normal high frequencies with a static pressure.
The effect of the static pressure on the hearing threshold was described
already in 1972 (Mach&Kessel), and reducing a sensitivity at low
frequency's (not influenting high's). Later Bekesy (see: Experiments of
hearing, p.360 Fig. 9-49), Disheck and also Rasmussen confirmed (in 50's ?)
that highs are by small positive pressure even amplified (8 dB or so).
In "normal language" - reduced loudness , exactly what happens in AC.
Also, my old professor explained always that the threshold of hearing is
already optimized and more sensitivity would cause hearing own heartbeat at
lows, brownian movements of air, and blood stream in capillaries. I really
don't remember what was responsible for 3kHz or higher.
Dr. Ribic Technisches Buero GmBH
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