Handbook for Sound Engineers

1378 Chapter 35

All simulation programs today are widely lacking the
algorithms required for computing the acoustical feed-
back. These, however, should soon become available,
since the available microphone data is similar in struc-
ture to that of loudspeakers, see Section 35.2.1.2. Then
it will be possible to calculate the maximum and
nominal acoustical gain based on the parameters of
microphone/loudspeaker/listener/talker, which take into
account the number of microphones and/or the arrange-
ment of loudspeakers.

35.3.4.3 Time Arrivals, Alignment

A graph of time arrivals (direct, direct + reflected,
reflected only) should allow the user to show the first
energy arrival as required by the design, to adjust a sig-
nal delay loudspeaker to bring the loudspeakers into
synchronicity, and to realize an acoustic localization of
an amplified source—via distance and the HAAS effect,
see Figs. 35-50A and B.
Matters are often complicated by special require-
ments such as localization, stereo imaging, etc. Simula-
tion programs allow determining the first wave front as

well as calculating initial time delay gaps or echo detec-

tions (c.f. in this respect Figs. 35-51A to C).

Predicted array lobing patterns of arrayable loud-

speakers should be displayed by simulation programs,

with the ability to provide signal delay and/or move the

appropriate loudspeakers to attempt to bring the array

into acoustic alignment. A program today will have the

ability to provide signal delay to the individual loud-

speakers to align them in time. The corresponding

sound pressure calculations will take into account either

measured phase data for the individual loudspeakers or

the run-time phase if phase differences among the

components can be neglected.^56

Fig. 35-52A and B shows the frequency response of

nonaligned and aligned loudspeaker groups, simulated

by EASE/ULYSSES.

35.3.4.4 Mapping, Single-Point Investigations

Once the aiming, power setting, and alignments are

completed, the program should provide a colored visual

coverage map of the predicted sound system perfor-

mance. This coverage map must take into account the

properties of the loudspeakers as well as the impact of

reflecting or shadowing planes, and provide the follow-

ing displays at a minimum:

Figure 35-48. 2D aiming mapping in EASE 4.2.

Figure 35-49. Waterfall presentation in EASE 4.2.

Figure 35-50. Delay presentations in simulation programs.

A. Reflectogram in ULYSSES 2.3.

B. Delay pattern of first arrival in EASE 4.2.