{'fraction_non_alphanumeric': 0.02021772939346812, 'fraction_numerical': 0.0038880248833592537, 'mean_word_length': 5.157894736842105, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A finite element model of the Japanese koto constructed from computed tomography scans.

This paper presents a method for using computed tomography (CT) scan images of a Japanese koto as the basis of a mesh of a finite element model. The CT images gave access to previously inaccessible internal geometry. Images of grain structure and orientation in all three dimensions of the koto's Paulownia wood was important to the model's development. Obtaining the wood's physical properties for the Voigt notation and using curvilinear coordinates to rotate it to account for the grain was also a critical step. Following the model construction, studies were conducted to investigate the koto's fundamental vibrational behavior. First, the model predicted the koto's mode shapes and frequencies. Simulations in the frequency and time domains also identified unreported aspects of the koto's acoustics. Second, five physical experiments were conducted including transducer studies, Chladni patterns, an acoustic camera tests, and the response of the koto when played. The acoustic camera in particular gave insights into the koto's sound radiation. The combined results advance the limited knowledge of the koto including identifying 100 Hz as the first eigenmode and 85 Hz as a major air mode.