Microphone system optimization for free fall impact acoustic method in detection of rice kernel damage

An impact acoustic free-fall setup was developed to distinguish the difference between the frequency of undamaged and damaged rice kernels using frequency analysis. The study determined the different design parameters of the impact acoustic system that would classify undamaged and damaged rice kernel for a particular/specific microphone. Two cardiods and one hypercardiod (AKG CK 91, Neumann KM 184, and Shure Beta 58A) microphones were used for this study. All three microphones underwent the experimental test which determined the appropriate distance of each microphone, and drop height of the samples from each impact surface (acrylic glass and metal). Results produced different peak amplitude outputs for each acoustic setup. The study also showed distinct frequency signature for both undamaged and damaged kernels. Validation experiments produced 93.3%, 91.1%, and 88.9% recognition accuracy for the three microphones, respectively. (C) 2012 Elsevier B.V. All rights reserved.