Durian Ripeness Striking Sound Recognition Using N-gram Models with N-best Lists and Majority Voting

Durians are green spiky fruits, which are considered as a delicacy throughout Southeast Asia. They are valued for their unique flavor and powerful taste. It is desirable to be able to determine the quality of durians without cutting them because it is difficult to quantify the ripeness from the external appearance and they are expensive to purchase. In Southeast Asia and China, consumers have found that after buying and cutting durians, they are not ripe or ready to eat. Therefore, studying striking signal characteristics and developing an automated method of recognizing durian ripeness levels without cutting or destroying them could benefit consumers of the fruit. The following method of recognizing durian ripeness by studying striking signals using N-gram models with N-best lists and majority voting is proposed. The recognition process is composed of three stages: 1) extract the acoustic features from the striking signals, 2) recognize unripe and ripe durian striking signals using the N-gram models and 3) find the ripeness from the N-best lists using majority voting. The results indicate that using the 3-best lists and majority voting method it was possible to recognize durian ripeness efficiently. Average ripeness recognition rates of 95.8%, 90.4% and 93.1% were obtained from the untrained, unknown and both test sets, respectively. The results demonstrate that the method is accurate enough to be used by consumers to help them select a ripe durian.