This series of curves shows how KEMAR's frequency response varies as
the source moves around in the median plane. Note that the broad ear-canal
resonance around 4 kHz doesn't change. However, the frequency of the pinna
notch changes significantly with elevation. It goes from a bit below 6 kHz
at low elevations up to 10 kHz or so as the sources moves overhead. When
the source is directly above, the notch is hard to see, and the frequency
response is fairly flat. It reappears as the source moves around the back
of the head and back towards the floor.
We should hasten to add that the detailed behavior of the pinna features
is quite sensitive to pinna shape, and varies considerably from person to
person. With larger ears, the frequencies are shifted lower. Other shape
changes introduce other significant changes in the response. This makes
it much harder to control elevation than azimuth in HCI applications.
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