Figure 5: The
NC curve shows
a frequency-weighted graph
of ambient noise
characteristics of
the space.
channels, closer spacing, etc.
The advent of digital television and
smartphones has produced challenges
for wireless transmission. An RF consultant can lay out a strategy to avoid
the common pitfalls.
Figure 6: An RF survey can aid in the selection and location of wireless components.
usually the HVAC system (heating and
air conditioning) and traffic noise.
A noise criteria (NC) measurement
can show the designer what they are
up against. The noise survey should
be done at a number of seating positions and the system designed around
the worst one. If the noise is excessive
(more than NC 40 for an auditorium,
for example) steps should be taken to
control it. This is another good time to
bring in a specialist.
Figure 5 shows a noise criteria survey
at a rear seating position in the space.
RADIO FREQUENCY
Here’s one that is sometimes overlooked.
The proliferation of wireless prod-
ucts in the audio marketplace makes a
radio frequency survey of the site a use-
ful endeavor. The number of wireless
products used in a room - particularly
in larger venues like auditoriums - tends
to escalate with time.
STANDARDIZE, FORMALIZE
A knowledge of the decay characteristics of the space is essential to selecting
and placing the appropriate loudspeaker
system(s).
The impulse response in its various
forms describe these characteristics. The
modal response can reveal problem frequencies for a particular space and can
aid in the placement of front of house
equipment as well as reveal the need for
room treatment.
A noise survey reveals how much
acoustic gain must be designed into
the system, and can reveal excessively
noisy sources that should be corrected.
A radio frequency survey is invaluable
for establishing a long-term strategy for
the implementation of wireless devices
in the space.
The ability to perform and interpret
a survey of this type is the mark of a true
audio professional. The required time is
rewarded by better working designs and
a good reputation.
A number of instrumentation platforms exist that are cost-effective and
widely available. They include PC-con-trolled dedicated instruments, hand-held
instruments and software applications.
Customer confidence increases as less
money is wasted on inappropriate equipment for the venue.
Site surveys are a major step in standardizing and formalizing system design
practices. n
Pat & Brenda Brown lead SynAudCon,
conducting audio seminars and workshops
around the world. For more information
go to http://www.synaudcon.com.
