Do all kind of vibrations follow simple harmonic motion rule? Please edify. - Page 1
Forum section: electronics / beginners

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 03:47:04 pm
content: Hi to everyone,From infinitesimally small waves like gamma radiations to very large RF wavessay, 10 kilo cycles, do all waves exhibit SHM principle? Thanks

author: IanB
author_rank: Super Contributor
timestamp: November 07, 2016, 03:54:34 pm
content: Yes, and no.Yes: are all waves made up of sine waves? Yes.No: do all waves look like a pure sine wave? No.In particular, consider sound waves from musical instruments. Many instruments can play a middle C (the same fundamental frequency). But all of them sound different (the sound waves on an oscilloscope all have different shapes due to the presence of different harmonics).

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 04:00:27 pm
content: I would have thought the fundamental frequency being same, it would be the multiples or submultiplesof fundamental frequency that impart characteristics peculiar to musical instrument of origin

author: XynxNet
author_rank: Regular Contributor
timestamp: November 07, 2016, 04:18:19 pm
content: In the real world you have usually more than one degree of freedom, superposition, different damping for different frequencies, etc.That's the reason why music instruments sound different. Harmonic motion rule is still valid but there is no longer anything simple about it.The beautifull thing is, you still can model and analyze these systems within the "simple model" using fourier transformation. You just get a bunch of superpositioned osczillations instead of a simple sine wave.(Fourier transformation is in my opinion one of the most astonishing and beautiful mathematical concepts. Especially because it basically reduces any fourier transformable function into variants of the complex exponantial function.)

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 07, 2016, 04:39:21 pm
content: Quote from: IanB on November 07, 2016, 03:54:34 pmAll waves can be approximated to any desired degree of accuracy over an arbitrary interval by an assembly of sine waves. Whether this means they are made of sine waves is a philosophical question.I would say that not all waves are harmonically related. For a relatively accessible example, take the x position of a chaotic pendulum. If all of it's motion was harmonically related it would be possible to write a time dependent equation for the motion. As far as we know this is not possible.

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 04:41:23 pm
content: Thanks for your reply XynxNet with a touch of philosophical narration implicit within.Momentarily,we touched sound vibrations, but what is the principle behind propagation of all these waves?I not sure it is SHM but then they all share some properties in common

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 04:48:00 pm
content: Quote from: CatalinaWOW on November 07, 2016, 04:39:21 pmThanks for the reply. what then is the principle upon which propagation of ultra radiation can be be best understood?

author: DmitryL
author_rank: Regular Contributor
timestamp: November 07, 2016, 04:56:00 pm
content: Quote from: sainbablo on November 07, 2016, 04:48:00 pmI think, you can start from here:https://en.wikipedia.org/wiki/Maxwell's_equations

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 07, 2016, 05:12:11 pm
content: Quote from: sainbablo on November 07, 2016, 04:48:00 pmIf you limit yourself to propagation of electromagnetic radiation then it is all harmonically related. All propagation of em waves conforms to Maxwells equations which have simple sinusoidal solutions. That seems to me to be the best way to understand propagation of ultra radiation if ultra radiation means em waves to you. It will require some faith or mental gymnastics to believe that something can propagate with no medium. Don't worry, the world's best physicists grappled with this problem in the late 1800s when the Michelson-Morley experiments showed that there was no luminiferous ether to carry these waves.When you talk about sound waves the problem gets more complex. The basic, everyday sound is a compression wave which again can be described by a simple differential equation and results in simple harmonic motion. But any gas is a non-linear medium and very high amplitudes, explosions and other shocks can result in more complicated things happening. Still solvable, but much, much more difficult.You can add another layer of complexity to this by using the chaotic pendulum to modulate the em wave. Propagation is still the same simple Maxwell's equations, but the amplitude at any point in space can no longer be so simply predicted.The best way to understand all of this is to bite off little chunks at a time. Start with the simple propagation of a single frequency em wave. If you don't have a course in differential equations under you belt it would be very helpful to read up on those. There are on line tutorials that can give you what you need, or you can dive into university level stuff for free (Search MIT Open Courses for example), Once you are fairly comfortable with that start adding more detail that is applicable to the problems that interest you.

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 05:39:13 pm
content: Quote from: CatalinaWOW on November 07, 2016, 05:12:11 pmThanks for the link to Maxwell's equations. I went over it cursorily. I am trying understand, in simple terms,how are the ultra radiations propagated.Like stone thrown in pond causing appearance of waves in water?Like sound originating from human larynx causing air disturbances in front of mouth leading to propagation of soundwaves in air?Like electro magnetic waves in ether?What is not clear to me is what is the underlying principle of the propagation of ultra radiations likegamma radiations.The latest post by Catalina WOW explains a lot. The more I ran away from maths back again to it. But I prefer to be ahobbyist

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 06:43:08 pm
content: To CatalinaWOW,In your last post you make a brief reference "it will require faith or some mental gymnastic....."That made me recall a story, I do not remember the source, about the set up there, concerned with information gathering.Some of the sources they relied upon was faith healers, seers and clairvoyants, pressed in service to conjure upand describe images about the focussed countries. You can gather more details.Here is one such example where a highly sophisticated setup deemed a "faith imagined image" of distantobject of interest of some value.I have failed to understand the physical aspect of it but some "flashes" do occur if you are a determined individual.

author: IanB
author_rank: Super Contributor
timestamp: November 07, 2016, 06:45:48 pm
content: Quote from: sainbablo on November 07, 2016, 05:39:13 pmGamma radiation is electromagnetic radiation. It propagates just the same as light or radio waves.

author: sainbablo
author_rank: Regular Contributor
timestamp: November 07, 2016, 07:05:17 pm
content: Quote from: IanB on November 07, 2016, 06:45:48 pmI was putting forth "either it is " or "it is not" premiseSome have mentioned "partly it is" "partly it is not"I am in a "fix"

author: IanB
author_rank: Super Contributor
timestamp: November 07, 2016, 07:58:14 pm
content: Quote from: sainbablo on November 07, 2016, 07:05:17 pmThere is no question here. Gamma rays come from radioactive decay and are a form of high energy electromagnetic radiation. Like radio waves, visible light, X-rays and anything else on the EM spectrum.However, if you are considering cosmic rays in space, then these are high energy particles and are not EM radiation. Maybe that is where your question comes from?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 07, 2016, 09:56:28 pm
content: Quote from: sainbablo on November 07, 2016, 07:05:17 pmThe confusion may also come from the wave-particle duality views of the universe. Gamma rays, like all other frequencies of radiation behave in some experiments like discrete packages of energy - called photons. Other experiments demonstrate wavelike behavior, particularly interference. The answer is that both are true. At the same time. Another difficult thing to wrap your head around. Googling wavicles may give you some background that will help. Both views of how this energy behaves are useful in describing its behavior in some circumstances. I haven't come across a really simple unifying description, though if you keep pounding through the math and physics you will get closer.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 08, 2016, 12:39:31 am
content: This is a much more complicated, much deeper subject than you were probably expecting. So, I must ask, do you want the short answer or the long answer?The Fourier transform is not a physical process. It describes an arbitrary function (given some constraints) as a sum of sine waves. It is abstract and mathematical.Many transforms exist, and an infinite number are possible. There's no particular reason to favor one or another in general. It depends on what you want to accomplish, in the course of mathematical analysis.That said, the Fourier transform is useful for all linear wave systems, and for these systems, they can be said to rely on combinations of sine waves.Tim

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 08, 2016, 02:43:16 am
content: There are other things which may be the origen of the ambivalent comparisons between radio and "ultra radiation" which your other sources mention. One is the extreme scale differences between these radiations. Radio waves have wavelengths which may be measured in dozens of meters, and always are measured in units of millimeters or larger. Gamma radiations have wavelengths measured in picometers. Interactions with matter are fairly uniform when the dimensions of the matter are ether very short or very long with respect to the wavelength, but the behavior is often different in the two regions, and the transition region can be very interesting.So even though both radio and gamma are em waves, radio will bend around human scale objects, and generally can't discern atomic scale and smaller features. Gamma either penetrates or is blocked by human scale objects, but shows an immeasurably small tendency to bend (diffraction). But gammas can interact strongly with atomic and smaller scale objects.These scale difference effects can easily be experimented with, and demonstrated with a ripple tank. Compare the impact on the ripple waves of a wire or pencil (things smaller than the ripple wavelength), and things like a brick or row of bricks (things larger than the wavelength).

author: hamster_nz
author_rank: Super Contributor
timestamp: November 08, 2016, 07:03:17 am
content: One thing I am starting to appreciate is that waves require energy to transfer between two different forms - gravitational potential and kinnetic energy for a pendulum and so on.The mental model I have for photons are that they a little whirlpool in the electromagnetic fields wizzing around at the speed of light. The more energy in the whirlpool, the faster it spins. The size and shape of the whirlpool is defined by the properties of the fields, so for a given amount of energy they will all be identical.

author: sainbablo
author_rank: Regular Contributor
timestamp: November 08, 2016, 03:52:09 pm
content: Quote from: IanB on November 07, 2016, 07:58:14 pm

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 08, 2016, 04:32:44 pm
content: Quote from: sainbablo on November 08, 2016, 03:52:09 pm

author: sainbablo
author_rank: Regular Contributor
timestamp: November 08, 2016, 05:37:51 pm
content: Quote from: CatalinaWOW on November 08, 2016, 04:32:44 pm

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 08, 2016, 07:04:50 pm
content: If you describe the fields and currents in your body, they will follow Maxwell's laws. Whether you are following the minute electrical flows due to neuronal activity or looking at what happens when you use a cell phone next to your head. But due to the complexity of the shapes and the gradual changes in material properties it will be difficult to impossible to actually solve those equations and get any useful insight out of them. While it is, in principle, possible to solve them numerically, poor measurements on shape and material properties will lead to significant imprecision in the results. And even once you have the numerical answers we don't have the knowledge to apply. Knowing the values for the neuronal flows doesn't translate into knowing what movement occurs, or what sound is heard, or what pain is felt. Knowing field strengths and frequencies doesn't predict whether you will get cancer or not.There are some limited uses of Maxwell's equations, and of formulas and approximations derived from them in applications to humans. Penetration depth for RF for example, both in determining burn depth from high field exposure an setting exposure levels. Current flow (through Ohms law, a special case corollary of the Maxwell equations) and so on.That is what I am saying, that while the laws apply, they are not a particularly useful tool for understand or describing human behavior and physiological response in many cases. They are more useful, but still not the best tools, for describing cosmic rays.

author: Cerebus
author_rank: Super Contributor
timestamp: November 09, 2016, 12:59:05 am
content: Quote from: CatalinaWOW on November 07, 2016, 04:39:21 pmI'm not sure that it is a philosophical question. At some level, perhaps, but at a more practical level I would suggest it is a confusion between a physical system and a mathematical model of one.Consider a sound wave created by pulling a sticky surface (such as a violin bow) past the edge of a steel plate. You'll get a sawtooth wave as the plate is drawn back, slips and springs forward, is again drawn back and so on.There's no doubt that the physical pressure wave has a sawtooth form. You can model this as a weighted sum of a lot of sine waves but those are imaginary, you can't physically measure any sine waves without filtering (i.e. applying a mathematical transformation).Why I think it's important to pick up on this, is that I have seen, more than once, people confuse mathematical models with reality. To the extent that people start to arguefromthe mathematical model rather than from the underlying modelled system. Maths is a way to describe things, it is not, with the exception of pure mathematics, the thing being described.That pure mathematics can have properties that correlate with physical reality is the point where it goes back to becoming a subject for philosophy.Quote from: sainbablo on November 07, 2016, 03:47:04 pmYou've got to love somebody who wishes to be edified.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 09, 2016, 01:21:29 am
content: Quote from: Cerebus on November 09, 2016, 12:59:05 amI don't think we are far apart, and I totally agree with the difference between a model and reality. Your saw tooth violin sound though is a good vehicle for the philosophical discussion. These philosophical discussions become more important in the quantum electronics and nuclear physics realm where the mathematical models are really the only reality we have. Anyone ever seen a live quark? Or just some data that is consistent with a model.

author: hamster_nz
author_rank: Super Contributor
timestamp: November 09, 2016, 01:46:48 am
content: Quote from: Cerebus on November 09, 2016, 12:59:05 amI wouldn't be so sure. You can also extract frequencies through physical effects. Somebody humming can cause a tuning fork to vibrate, if they are tuned to the same frequency. Diffraction and refraction also can be used to filter physical waves - it isn't a purely 'mathematical' transformation.

author: Cerebus
author_rank: Super Contributor
timestamp: November 09, 2016, 02:08:05 am
content: Quote from: hamster_nz on November 09, 2016, 01:46:48 amBy introducing a mechanical filter or resonance you've altered the underlying physical system. The sine wave wasn't there before you did that. I did deliberately pick the physically generated sawtooth as something that doesn't,per se, have a physical fundamental sine wave like a plucked string.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: November 09, 2016, 02:14:10 am
content: On a related topic, this series on the Michaelson Harmonic Analyzer is very interesting:

author: sainbablo
author_rank: Regular Contributor
timestamp: November 09, 2016, 11:34:42 am
content: Quote from: sainbablo on November 07, 2016, 03:47:04 pmYou've got to love somebody who wishes to be edified."More than the calf wishes to suckle, the cow yearns to be suckled" A quote recalled, reading from a book of Physiology, decades agoin good old UK ( it still is)

author: sainbablo
author_rank: Regular Contributor
timestamp: November 11, 2016, 04:39:36 pm
content: After going through posts of all the participants if I put forth a conclusion thatphysical sciences like Maths, possess quality that is, its terrestrial results are predictable and as well areapplicable to study of various objects in outer space but in case of human beings its scope is limitedowing to the fact that human's structure being biological, limit Maths scope of applicability, am I rightcoming to that conclusion?

author: TimFox
author_rank: Super Contributor
timestamp: November 11, 2016, 05:49:40 pm
content: In a non-EM context, consider the overtone content of actual musical instruments. Overtones are the higher-frequency tones in a musical note, and are not necessarily harmonics.For one-dimensional instruments, such as vibrating strings and narrow organ pipes, the overtones will be very close to harmonics (integer multiples of a fundamental).For two-dimensional instruments, such as the kettle drum, the overtones are not harmonic.Seehttp://circularscience.com/about-drumsfor a discussion of overtones from a circular diaphragm.

author: sainbablo
author_rank: Regular Contributor
timestamp: November 11, 2016, 07:17:14 pm
content: Quote from: TimFox on November 11, 2016, 05:49:40 pmQuite so. My understanding is that the vibrations emanating from one or two dimension sources when striking the ear membrane assumea characteristic head setting ear membrane in to and fro motion ie towards interior( to wards middle ear) and outwards (towards the ear passage), which again is a replica of simple harmonic motion,and the membrane converts wave form to mechanical energy for transmission to internal ear.To generalize I would say that range of audible frequencies from 64 to just about 4096 c/s (general terms) is so perceivedNow each of these instruments have 'character' of its own so that even with eyes closed one would name the source.So violin, or drums, or harmonica, being some examples of string,percussion and reed instruments reveal their nature to the listener.My question is what is the basis of individuality of each of these instrument as is distinguished by the hearer?Conceeded that the output of strings have no recource to internal reflection as have pipe instruments producing over tones, yetear separates them.My idea is that the head of the wave form and its shape striking the ear membrane has role in it.What then, is the physical nature of that wave form?Here I may have some what deviated from main topic but even at the risk of cross purpose, perceiving your musical proclivity, Ifeel encouraged to invite your attention.

author: Loboscope
author_rank: Regular Contributor
timestamp: November 11, 2016, 10:29:35 pm
content: Hearing sounds is a task done by our ears, identifying sounds is a task done by our brain. Normally no one can identify musical instruments if he has not learned before, how these instruments will sound.But if you regard the hearing processes in our brain, you will become aware, that our brain is a champion in identifying sounds nevertheless how complex they are and how complex might be the hearing situation (for example when you talk to persons in a noisy environment). You can find lots of details about this item in this book: "Auditory Neuroscience - Sense of Sound", Jan Schnupp et al, MIT Press 2012.Musical instruments can be identified by two characteristics: one is the harmonic structure of the overtones, especially the individual patterns created by the different instruments/voices, the so called formant frequency (by the way: the cymbals are the musical instruments with the most inharmonic overtone structure, much more noise than sound, but the different cymbals will sound very different and characteristic and can easily be distinguished by a musical skilled ear).The other is the very complex and very individual pattern of the first moment when the tone starts resp. the tone is created by the player: the transient phenomenon (german: "Einschwingvorgang"). In this part of one second a relatively chaotic pattern of frequency, noise etc. may appear, but these patterns are very individual for any instrument etc. and will be an essential held for identifying the sound of the different instruments. For example: if you will cut this first initial moment of the tone and let only hear the steady sound afterwards, also skilled ears often will not more distinguish the sound of clarinet/oboe/ soprano-sax.