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AZIMUTH AND LOOK ANGLES
“Azimuth” refers to the horizontal angular offset of a real or virtual speaker from centre. “Look angle”
refers to the horizontal angles of the listener’s head while looking centre, left and right during the
PRIR gathering process.
The look angles for a PRIR are the left and right end points of the head tracking range. It is optimal to
have a range of ±30° for usability and tracking resolution.
For each new PRIR measurement, speaker azimuth values and look angles must be entered or
measured by the Realiser.
In the basic procedure given earlier in this manual, the speaker azimuth values were entered manually,
and the look angles were the same as the azimuth values of the left and right speakers. But they need
not be. In the instructions below, alternate methods of finding and logging azimuth and look angles
are described.
Logging look angles
During the
SPK
(PRIR) measurement, the listener looks in three directions: centre, left and right. The
look angles are subsequently used to create head-tracked virtual loudspeakers by interpolation between
pairs of these data points. The actual values of the look angles are important, and the Realiser provides
three methods for logging them.
Press
MENU-SPK
. The screen will say:
>SAVE AT END:YES
LOOK ANGLES:AZI
EXCITATION MENU
SPEAKER MODE MENU
In the
LOOK ANGLES
line are these choices:
AZI
(azimuth) -- The listener looks directly at the centre, left and right speakers, and the Realiser takes
the look angles to be the same as the speaker azimuth angles. This is the default method, described
earlier in this manual under Personalisation Basics. The correct azimuth of the front speakers will
have been entered manually (via
MENU-1
, etc. as described in I/O Assignment and Angle Entry).
The listener must be careful to point the head, and thus the ears, at the speakers. People tend to “turn”
the last few degrees by moving their eyeballs. A dominant eye can also bias the turning. For example,
a right-eye-dominant person will tend to look slightly left, attempting to centre the dominant eye.
When
AZI
is run immediately after
SPOS
, the azimuth values logged with that procedure will be used
for the PRIR rather than the angles entered manually.
The fact that speaker azimuth angles = look angles with
AZI
means that the head tracking range is
constrained by the left and right speaker placement. Fortunately, the optimum head tracking range of
±30° will be achieved with the typical left and right speaker locations of ±30°. However, if the left and
right speakers are closer together, as is typically the case when the front three speakers are all behind a
screen as on dubbing stages and in cinemas, the narrower head tracking range will be confining and the
user is advised to use the
HT
method below.
