Evaluation of individual differences of vibration duration of tuning forks

Kyota Nomizu – k-nomizu@chiba-u.jp
Sho Otsuka – otsuka.s@chiba-u.jp
Seiji Nakagawa – s-nakagawa@chiba-u.jp
Chiba University
1-33 Yayoi-cho, Inage-ku
Chiba-shi, 263-8522, Japan

Popular version of paper 2aMU5

Presented Wednesday morning, June 9, 2021

180th ASA Meeting, Acoustics in Focus

A tuning fork is a metal device that emits a sound of a certain frequency when struck. Tuning forks are used for various purposes, such as music, medicine, and healing. In addition to the fundamental frequency component, the harmonic tone appears immediately after struck, with a 6-times higher frequency. First of all, the accuracy of the fundamental frequency is needed. Additionally, the fundamental tone needs to be sustained for a long time, while the harmonic tone should decay rapidly. However, only the fundamental frequency is tuned in the manufacturing process of the tuning forks, durations of tones have not been evaluated. In addition, most studies on tuning forks have been about frequencies of tones or mode analysis, and those on the vibration duration are very limited.

 

Figure 1: Tuning forks used in the experiment.

 

In this study, we aimed to assess individual differences in the vibration duration of tuning forks. Also, we tried to clarify factors that affect the vibration duration. In this study, as a first step, we evaluated the effect of the holding force.

In the experiment, we struck four individual tuning forks of the same type and recorded their sound, and estimated durations of their fundamental and harmonic tones. Measurements were repeated with changing the holding force.

 

Figure 2: Evaluation of the vibration duration.

 

As a result, significant individual differences in the duration of fundamental and harmonic tones were observed. Especially, the tuning fork with the shorter length and the smaller mass had a shorter fundamental tone. Also, the duration of fundamental and harmonic tones varied depending on the holding force. The best holding forces for both tones were different for each tuning fork.

These results suggest that even for the same type of tuning fork, small differences in shape and heterogeneity of the material may affect the vibration duration. It is also suggested that there is a desirable holding force for each tuning fork that can achieve both a long duration of the fundamental tone and rapid decay of the harmonic tone.

 

Figure 3: Duration of the fundamental tone at each holding force range.

 

In the future, based on these results showing the relationship with the holding force, it is necessary to conduct a comprehensive study on the effects of shape parameters and environmental conditions such as temperature and humidity. It is thought that the results theoretically contribute to improving the manufacturing process of tuning forks, which currently relies on the empirical knowledge of artisans.

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