Vibroacoustic Analysis of Standing Bowls

Quek, Sze Qi (2024) Vibroacoustic Analysis of Standing Bowls. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Standing bowl is a type of musical instruments that produces a rich, deep tone when played and the exotic sound will continue to float for a long time. It is believed to have strong healing properties and promote relaxation. It is used by some wellness practitioners such as music therapists, massage therapists and yoga therapists during treatment. For different sizes of standing bowl, the vibroacoustic analysis of the standing bowl is not reported. The information about the large-sized standing bowls are still lacking. The playing method is by striking the standing bowl with a mallet while standing in it. There were 3 different sizes of standing bowls used as a test specimen in the experiment. In order to determine the vibroacoustic characteristics of the standing bowls, Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA) were carried out. The vibroacoustic characteristics were categorized into two categories which are vibration characteristics and acoustic characteristics. For vibration characteristics, impact testing was conducted with the apparatus set up and LMS TestLab software. The apparatus required for the experiment is the standing bowl, impact hammer, laptop which is the data acquisition system that equipped with LMS Impact Testing software, single axis accelerometer, accelerometer cable, and LMS SCADAS Mobile. Besides that, FEA was used to validate the results obtained from EMA. FEA was done by creating the finite element models in SolidWorks and they were imported to Ansys for simulation. The vibration characteristics of standing bowl were determined such as the natural frequencies, mode shapes and damping characteristic. For standing bowl A with the radius of 22.04 cm, the fundamental mode has the natural frequencies of 70.966Hz and the damping ratio of 0.10%. For standing bowl B with the radius of 25.78 cm, the fundamental mode has the natural frequencies of 48.893Hz and the damping ratio of 0.30%. For standing bowl C with the radius of 27.05 cm, the fundamental mode has the natural frequencies of 49.191Hz and the damping ratio of 0.25%. For acoustic characteristics, the sound measurement was conducted with the apparatus set up and LMS TestLab software. The apparatus used in the sound measurement is similar to impact testing since only the impact hammer is replaced by microphone and mallet. The sound measurement was conducted in a quiet environment for obtaining accurate results. The results obtained include sound spectrum, acoustic response graph, spectrogram and power spectral density.For standing bowl A, the decay time is the shortest which is 114.05 s. For standing bowl B, the decay time is 165.5 s. For standing bowl C, the decay time is the longest which is 180.76 s. The vibroacoustic characteristics of standing bowls were then compared between the 3 different sizes of standing bowls in order for the therapist to select the appropriate frequencies and mode that allign with the therapeutic purposes and preferences of the clients.