Virtual Systems 1455the gain up higher in the most critical loudspeaker zones
while not increasing the gain everywhere, thus keeping
the overall system stable.
A virtual sound processor may have many thou-
sands of controls that need to be adjusted during a
systems initial setup. Today’s advanced virtual proces-
sors contain control tools that allow the system commis-
sioning engineer a much simplified interface for
adjusting those controls. This greatly reduces the time
required and the chances for error in setup.
In short a well-designed virtual sound system can
apply all the little tweaks to the system’s controls that a
very skilled operator would have applied if he or she
could respond to conditions in a split second and adjust
hundreds of controls at once.
38.4.4 Active Acoustics
The virtual sound system may also be used to modify the
acoustic environment.
The reverberation time and reflection patterns of the
space may be dynamically varied at any time to meet
the needs of the program material. This requires that the
physical acoustics of the space be at the low end of the
desired reverberation range. The virtual sound system
will add the initial reflections from the proper spatial
directions, and the enveloping reverberant tail, to
produce the desired acoustic environment. The ability to
change the acoustics on an almost instantaneous basis
allows each portion of a program to be performed in its
optimum acoustics. For example, spoken portions of the
program may only utilize a few supportive reflections.
At the other extreme, choral or organ music may have a
very long reverberation time. This technology may also
be used to simulate the acoustic environment of the
room in outdoor performance venues.
Environmental noise, particularly that of a low-
frequency and/or repetitive nature, may be actively can-
celed by the virtual sound system. As the cost of DSP
processing comes down, and the power handling of
transducers goes up, this technology will become more
attractive in comparison to traditional noise control and
isolation methods. Vibration and low- frequency sounds
are the most difficult and costly to isolate using tradi-
tional passive methods. High displacement isolation
mounts together with large amounts of mass are often
required for good low-frequency performance. At
higher frequencies often far less expensive techniques
and materials are effective. By comparison, active noise
and vibration control techniques are most effective at
the lowest frequencies, but find it increasingly difficult
to obtain satisfactory performance over large areas at
higher frequencies. Therefore, including active noise
control techniques in a virtual sound system to control
low-frequency noises may prove beneficial in reducing
the total project cost.38.4.5 DiagnosticsThe virtual sound system will monitor its own operation,
and the environment in which it operates. The entire sig-
nal path will be monitored for failures. Depending on the
level of system design, the operator may just be notified,
or redundant equipment may be automatically utilized to
assure uninterrupted operation. Most systems will utilize
multiple microphones and loudspeakers. In itself, this
provides a significant degree of redundancy. If the cover-
age pattern of the microphones or loudspeakers is con-
trollable, then the virtual system can compensate for any
given failure of a microphone or loudspeaker. Redun-
dancy may also be designed into the interconnections and
processing subsystems of the virtual sound system. With
careful design, systems with few or no single points of
failure can be built.
Environmental conditions that will impact the long
term health of the system, such as temperature and
airflow, will be monitored and trends logged. The perfor-
mance of the microphones and loudspeakers in the
system will be monitored and recorded to spot degrada-
tion of performance before it becomes audible. The
acoustic environment will also be monitored to spot
changes that might impact on the subjective performance
of the sound system. System health reports will be auto-
matically generated and sent to the system operator,
installer, and designer when any of the parameters moni-
tored are outside of expected tolerances. This capability
will result in much more consistent performance over the
life of the system, and will extend that life for years.38.4.6 The Sound System of the FutureWhen all these techniques are combined, the virtual
sound system of the future will have better performance,
be more invisible to the user, be easier to operate, and
have a longer life than any current system.