We regard every layer of grain as a lot of Helmholtz resonators in parallel, and regard different layer of grains as the paralleling resonators in series.

• 一定厚度的粮食可看作是一种组合式共振吸声结构，每层认为由许多个单独亥姆霍兹共振腔并联而成，而层与层的共振腔为串联关系，表现为共振性吸收，出现了共振吸收峰。