Abstract: A sound isolation plate structure comprises a sheet of perforated board in which a plurality of holes are formed, and cylindrical portions provided on one surface side of the perforated board to extend from peripheral portions of the holes like cylinders unilaterally, wherein pneumatic vibration systems are formed between the cylindrical portions. Accordingly, a resonance frequency of vibration systems is easily tuned by adjusting a projection amount of the cylindrical portions so as to mate with a frequency of the noise to be isolated.

Abstract: An airflow type sound isolation plate structure comprises two sheets of plate members positioned in parallel at a predetermined interval. One of plate members is arranged on an air inlet side and the other of plate members is arranged on an air outlet side. Plural sets of first opposing holes and plural sets of opposing second holes are provided in two sheets of plate members respectively. Peripheral areas of respective sets of first holes are connected by cylindrical connecting portions so as to form a continuous hole in their internal spaces. Annularly extended portions are provided to peripheral areas of respective sets of second holes so as to oppose to each other and not to contact to each other. Internal spaces are provided around the annularly extended portions between both plate members. Inner peripheral surfaces of the first holes and the second holes formed in one of plate members are expanded gradually toward the upstream side of air flow.