Spatial hearing (Blauert, 1997) is accomplished by two ears sampling
the acoustic field through small apertures (ear canals) having
diameters smaller than the wavelength across almost the entire audio
band. As a result, the directionality of a sound is inferred primarily
from the relative intensity (
) and time-of-arrival (
) at the two
ears. There is also directionality information impressed on the
signal by pinnae filtering and shoulder reflections, etc., that are
especially important for elevation perception.13For azimuth perception,
is the dominant cue below about 800 Hz, and
dominates above 1600 Hz or so.14In the octave between these
limits, both
and
are used. Also,
is picked up as
phase delay for low frequencies, and group delay at high
frequencies (ibid.).
Perceptual accuracy is on the order of 1
for azimuth in
front of the listener. The lower limit of azimuth perception based on
is approximately 80 Hz, below which phase differences become
imperceptible. Thus, our spec is to synthesize correct
s down to
80 Hz. Note, however, that since the acoustic wavelength at 80 Hz is
over 4 meters long, we could get by with reduced spatial resolution in
this frequency range, such as simple stereo. Multiresolution speaker
arrays are discussed starting in §4 below.
http://arxiv.org/abs/1911.07575
.