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ZORBA is a
computer program for predicting the sound absorption of common acoustic
materials such as fiberglass, mineral wool or polyester. The effect of
perforated or slatted coverings can be predicted as can that of panel
absorbers. The properties can be predicted by knowing the flow resistivity
of the material and its thickness and the dimensions of the slots or
perforations. The flow resistivity is a measure of the resistance to steady
airflow and can be readily measured (ASTM C522) or for many materials can be
estimated from the density and fiber diameter. Various models for predicting
absorption have been developed over the years. |
ZORBA
gives a choice of different models but by default uses
Allard and Champoux’s model (JASA Vol 91 1992) which is the most accurate
simple model currently available for predicting absorption. The model is
accurate for high porosity materials (i.e. most common acoustic absorbers)
when predicting normal incidence absorption. The program has the unique
ability to predict random incidence absorption taking into account the
variation of absorption with angle of incidence and the diffraction by the
edges of the material. Within limits this will give a good estimate of the
absorption that would be measured in a reverberation chamber . The
performance of slot absorbers, perforated facings and panel absorbers may be
predicted by entering the physical dimensions of the slots or holes. A
combination of two materials of different flow resistivity and thickness can
be modeled. |
