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2. At any given point there should be at least 3 speakers with a clear line of sight to the
tracker microphone. Three readings are needed to triangulate the tracker position in
3D. If the speakers are all placed on one side, or if the tracker is worn where it could
be blocked from more than one speaker at a time the tracking will stop until it receives
pulses from at least 3 speakers.
3. The speakers should be as far apart from each other as possible. If two speakers are
too close together there is a very high probability that they will be blocked
simultaneously and stop the tracking.
4. The tracker should not be too close to any speaker because there would be too
much loudness from that speaker compared to the other three. As a rule of thumb try
to set up the speakers so that the tracker is at least a couple of metres away from all
speakers.
5. Consider sampling rate issues, discussed in the next section of this chapter.
6. The imaginary surface formed by the four speakers should never be crossed by the
trackers. For example, setting the four speakers at a height of 1.60 m would be very
risky because the tracker could easily move under or over that height and cross this
imaginary plane (plus you would probably have problems related to issues 1 and 4
above). When the plane is crossed the tracking system is turned inside out and erratic
behaviour is observed.
7. While the MLD has a robust echo detection and rejection system, it is advisable to
mount the speakers away from walls when possible to avoid echoes bouncing off the
walls and causing pulse detection problems. Under ideal circumstances, mount speakers
3 or more metres (10 feet) away from each wall. Mounting speakers in corners is
particularly bad; if it is not possible to be 3 metres (10 feet) away from all walls, it is
better to position them closer to the centre of the room away from the corners.
8. Please note that the following issue is NOT as important as issue number 1, above. A
speaker should be tilted so that it is pointing to the farthest point in the interactive area
that its pulses will have to reach. The reason for this is that the speaker's sound
emission is not uniform and we want the region of strongest radiation (along an axis
directly out from the centre of the speaker) to be pointing where it will need to travel
most. Again, issue number 1 in this section is much more important than this issue.
With these issues in mind you can understand the drawbacks in all possible situations.
Here are a few examples of acceptable configurations.
Page 78
MLD manual 1.1
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