About The Doppler Parameters - Lexicon LEXICON480LV4 Owner's Manual

Page One
PLAY
Play Trigger
Page Two
PLAY
Play Doppler
The Doppler Program
Everyone is familiar with the Doppler effect heard when
a train or truck goes zooming by. The Doppler program
recreates this effect with startling realism by reprod-
ucing the panning, amplitude and pitch variations
heard as a sound source moves past the listener.
These programs were designed specifically for film
and video applications. An audio trigger allows the
Doppler to be cued into a mix. The Cascade mode
allows audio to be captured and looped in a sampling
program in Machine A, and a Doppler program to be
loaded into Machine B that will trigger the effect. Try
very short times (one second or less) and small dis-
tances (0.3 meters) to produce an illusion of a sound
zooming by your head.
Note that using a combination of high settings for all
parameters can result in noise and aliasing becoming
audible.

About the Doppler Parameters

Page One
PLAY (Play Trigger)
When triggering the doppler effect manually, press
PLAY to trigger. The sound must have started at some
time before PLAY is pressed. This is called memory
preload and is equal to the amount of time it takes the
sound to travel from the starting point of the object to
the listener. The amount of time required depends on
the settings of SPEED and TIME. At maximum speed
and time the sound must be started up to 1.3 seconds
before PLAY is pressed. At minimum SPEEDs and
TIMEs, the time needed to preload the machine's
memory is quite short.
If an audio trigger has been set up on page two,
pressing PLAY does not start the effect immediately;
it arms the effect, and then waits for the appropriate
level to start the effect. The memory preload time is
built in, so the effect starts shortly after the trigger.
TYP FG
Play Type Amp Q/Pch Q
Bank 8: the Pitch Change and Doppler Programs
TIM
SPD
Time
Speed
TYPE (Play Type)
TYPE affects the rate of change of the level of the
sound. It has two modes--NORMAL and ZOOM. In
NORMAL, the level is inversely proportional to the
distance from the object to the listener. The object
moves in a straight line from one side to the other. In
ZOOM, the level is inversely proportional to the dis-
tance squared. The sound moves in a parobola, mov-
ing rapidly toward the listener and then away.
FG (Fudge Factor)
FG is AMP Q/Pitch Q * 64. The amplitude Q (i.e., the
sharpness of the amplitude increase as the object goes
by) is set only by DISTANCE Q. When FG is set to 64,
the pitch change follows the amplitude change in a
theoretically accurate manner. Sometimes it sounds
better to have the pitch vary more gradually. This can
be achieved by raising FG. For example, when FG is
set to 128, the pitch acts as if the object is twice as far
away, while the amplitude remains at the distance set
with DISTANCE Q.
SPEED
SPEED sets the total pitch shift that will occur. When
SPEED is set to 0, there will be no pitch shift. The pitch
shift set with SPEED is quite accurate.
TIME
TIME sets the time between when the device is trig-
gered and when the sound is midway between the two
loudspeakers.The total time of the effect is twice the
value set with TIME. TIME has great impact on per-
ceived speed. Short times and small distances make
the object appear to be moving quite fast.
DISTANCE Q
DISTANCE Q sets the sharpness of the effect in both
amplitude and frequency. The control displays the
distance of closest approach, and the displayed dis-
tance depends on the TIME selected. For an accurate
emulation of a real event, time should be set first.
DST
Distance
TRIG
Trigger Doppler
7-5