Tuning Fork Physics - Part 2: modal analysis using FEA

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Recommends N. Virgo · 2013-01 · Physics Stack Exchange · on “Why don't tuning forks have three prongs?”

The reason for having two prongs is that they oscillate in antiphase. That is, instead of both moving to the left, then both moving to the right, and so on, they oscillate "in and out" - they move towards each other then move away from each other, then towards, etc. That means that the bit you hold doesn't vibrate at all, even though the prongs do. You might ask why it is that they do that, instead of oscillating in the same direction as one another. The answer is that at first they oscillate in both ways at the same time, but the side-to-side oscillations are rapidly damped by your hand, so they die out quickly, whereas the in-and-out ones are not damped this way, so they ring on long enoug

Recommends Sean E. Lake · 2017-04 · Physics Stack Exchange · on “How pure is the tone produced by a typical tuning fork in air?”

One way to see answers to this question is to enter "tuning fork spectrogram" (without quotes) into a search engine. The answer, qualitatively, is fairly pure, after the initial high pitch transients from striking it die out. In the spectrograms presented in this work (Douglas Lyon, “The Discrete Fourier Transform, Part 5: Spectrogram”, Journal of Object Technology, Volume 9, no. 1 (January 2010),pp. 15-24) [LINK] , Figures 4 and 5, the tuning fork clearly has both overtones and undertones present in the spectrogram. Qualitatively, though, Figure 4 (the one with a linear stretch) makes it appear that the fundamental is very dominant, probably at least a factor of 2 louder than the nearest ha

Cites ghoppe · 2013-01 · Physics Stack Exchange · on “Why do tuning forks have two prongs?”

Q. How do two coupled vibrating prongs isolate a single frequency? howstuffworks.com has an article on How Tuning Forks Work [LINK] The way a tuning fork's vibrations interact with the surrounding air is what causes sound to form. When a tuning fork's tines are moving away from one another, it pushes surrounding air molecules together, forming small, high-pressure areas known as compressions . When the tines snap back toward each other, they suck surrounding air molecules apart, forming small, low-pressure areas known as rarefactions . The result is a steady collection of rarefactions and compressions that, together, form a sound wave. The faster a tuning fork's frequency, the higher the pit

Cites Gilbert · 2025-04 · Physics Stack Exchange · on “What is modal analysis?”

Modal analysis is a general tool to help engineer structures subject to vibrations. Suppose you are engineering some mechanical structure (car, airplane, wind turbine, bridge, tuning fork, etc., etc., etc.). Susceptibility to vibrations can be, alternately, the point [LINK] of the structure or a real problem [LINK] . Understanding the natural oscillatory modes (including the frequencies and the mode shapes) is often critical for engineering for performance, robustness, safety, and cost. Taking the tuning fork as a simple example, suppose we want to engineer it such that it rings with a fundamental mode at a particular frequency, but we want other modes at other frequencies (various overtones