Circular Membrane (drum head) Vibration

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A circular membrane (drum head) vibrates with a variety of interesting patterns and shapes, each at their own frequency. In this demonstration I took a 6-inch square of latex rubber dental dam (courtesy of my dentist), stretched it over a short length of 4-inch diameter PVC pipe, and held it in place with rubber bands. I drew some lines and circles on the membrane to help identify vibration shapes. A frequency generator (you could use a computer) provides a sine wave to a loudspeaker. A strobe light was used to "slow down" the vibration so that it is easily visible. The flickering in this video is the result of mistiming between the strobe light and the video camera frame rate.

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14 окт 2024

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Комментарии : 44

@kidzbop38isstraightfire92 2 месяца назад

Excellent video!! Was looking at Helmholz equations and came across this..well done!

@riemanntensorfan Год назад

I was looking at Helmholtz equation example with a drumskin at Mathematical Methods for Physics and Engineering book, and they expose exactly the same modes of oscillation you show us here. Thanks for the video!

@loiswilcken1758 3 года назад

What a wonderful discovery! I worked for many years with a master drummer from Haiti and am now writing his biography. He's passed away, so I can't ask questions now, but I can listen to his best recordings and study their spectrograms. He always said, the drum is a piano, and I want to make sense of that. This kind of basic knowledge will help.

@flayy5750 3 года назад

Those are some very powerful words; thanks for sharing, and good luck with your work : )

@mem1gui 7 лет назад

Thank you so much for this video. I teach introductory Acoustics and I do a lab on this topic, and it is really helpful to have a slow-motion video of different modes so you can actually see what's going on. I also love all your acoustics animations on your university web page. Such a wonderful resource to give the students visual pictures of the physics. Thank you, thank you, thank you.

@DanRussellPSU 7 лет назад

Thanks! I'm glad you find them useful.

@lucanicolaquaroni858 4 года назад

Many thanks Dan! I find your physical demonstrations as well as the animations on your web page extremely useful; you have excellent teaching skills! I especially enjoyed this particular video since it's the closest thing I can visualize to the higher order acoustic modes of circular cylindrical ducts: amazing!

@alexigirgis 11 лет назад

This is because of the offset weighting of the Indian Tabla. Breaking the radial symmetry of the drum head causes once degenerate modes (two modes with equal frequency) to split into distinct modes each with a different frequency.

@yqisq6966 2 года назад

Hummm interesting usage of strobe light. It's like slow mo video without actually using expensive slow mo camera.

@arahman3897 3 года назад

It looks amazing.

@cryora 8 лет назад

You mean the strobe light is there to only show the drum at "continuous" phases but at different periods, and at a rate slower than how the drumhead actually evolves in time.

@DanRussellPSU 8 лет назад

Yes

@cryora 8 лет назад

+Dan Russell Clever!

@34672rr 8 лет назад

+Dan Russell why is the fundamental at that particular frequency? Is it due to the tension and trial and error? or did you know it would be at that pitch?

@cryora 8 лет назад

Roughly speaking, probably from solving the wave equation in cylindrical coordinates, and applying boundary conditions to obtain different eigenmodes (discrete wavelegths). Then from Fourier Analysis of the waves, a dispersion relation can be found.

@34672rr 8 лет назад

***** trial and error would be much easier. Just turn the frequency knob until you get the fundamental mode

@WALID0306 Месяц назад

great !

@raguks 12 лет назад

Amazing. Do you know which of these modes contributes to the tunable frequency we hear? That is when we tune which of these modes are we hearing for among 1,1- 2,1 - 3,1 etc?

@PhantomKING113 5 лет назад

I believe it's the first one, but if the drum is too big you might not be able to hear that one.

@thebladeitself 11 месяцев назад

this is so F&$*ing cool!

@johnroberts4178 11 лет назад

Real drumheads vibrate in exactly the same vibration modes but the amplitude or physical excursion is much smaller so they do not make such pretty videos.

@vtmike13 14 лет назад

@SpartanDFM18 ehhhh hahaha maybe. i want to work with drumheads in the future as a material science engineer. i probably won't use partial differential equations, but maybe some ODE's.

@Karun1793 13 лет назад

Can you please tell me what makes the membrane vibrate? Cause, i need to show a similar phenomenon for my architectural design project.

@PhantomKING113 5 лет назад

The speaker causes sound, which coincides with the frequency the membrane vibrates at. This causes small vibrations to build up into a larger one. It's resonance.

@woopswoopswoops3942 2 года назад

could someone please explain what is happening and why it's happening? thanks in advance :))

@PhantomKING113 5 лет назад

I just wanna know the frequencys. Let's say the first mode vivrates at 440 H. What are the harmonics?

@kuggn 4 года назад

440 is "a", harmonics in the tonleiter?

@vtmike13 14 лет назад

@Alienated29 you'd be very surprised actually

@PavelRzhepishevskiy 2 года назад

Thanks!!! :)

@SergeantNichols 5 лет назад

What is the general solution for the first mode (0,1)?

@MrKingss 6 лет назад

How many frames per second was this video recorded in? 240?

@DanRussellPSU 5 лет назад

30 fps => but A strobe light was used to "slow down" the vibration so that it is easily visible. The flickering in this video is the result of mistiming between the strobe light and the video camera frame rate.

@sickleandsuckle 6 лет назад

It's weird because quantum confined particles will have wavefunctions that look just like this!

@DanRussellPSU 6 лет назад

Actually not so weird -- the math is the same for both problems. That's what makes physics so fascinating (to me at least) -- the similarities in so many different applications.

@sickleandsuckle 6 лет назад

Well i mean the similarities are weird when you really think about. the fact that a particle's quantum "presence" can be described with this same sort of math and phenomena.

@moiquiregardevideo 6 лет назад

The point to find these analogies is precisely to understand what matter really is. Without fully understanding every detail, we can say that frequency and resonnant modes are fundamental parts of matter.

@adamfarris1458 5 лет назад

The motion of both can be derived from the associated Helmholtz equations, using Bessel functions to calculate the various eigenfrequencies.

@jorrelyanga647 11 лет назад

destiny

@wavewizard1711 6 лет назад

See animation vibrating circular membrane with freeware WaveWizard: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-H6ZVXzltfew.html

@rutherfordbynes1757 5 лет назад

who else here is being disturbed by the video blinks?

@DanRussellPSU 5 лет назад

If you read the description . . . A strobe light was used to "slow down" the vibration so that it is easily visible. The flickering in this video is the result of mistiming between the strobe light and the video camera frame rate.