What a tremendous difference a little thing like the type of paint used on the concrete block walls makes! This is a primary lesson to be learned from this chapter. Unless one has the resources to set up to test a concrete block wall and to measure the absorption coefficients of the specific blocks to be used, it is better to paint the stuff with a heavy paint and depend on known materials. If your heart is set on using the absorption of a particular local concrete block with its natural surface, another approach would be to approach the treatment of the room in increments, measuring reverberation time step by step as materials are added until the desired characteristics are achieved. Most of us do not have the means, the patience, or the love for certain concrete blocks to justify this.
