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Topic: Natural frequency

In the News (Thu 16 Feb 12)

EXECUTIVE POWER

Iran

ANALYSIS

Pakistan

Family compact

	BOSS Model
		Resonance is a buildup of amplitude in a physical system that occurs when the frequency of an applied oscillatory force is close to the natural frequency of the system.
		In the case of an earthquake, the ground shaking may be at the same frequency as the natural frequency of a building.
		The taller the rod, the lower the natural frequency.
	www.wested.org /werc/earthsystems/geology/boss.html (1851 words)

	Natural Frequency
		A key aspect of structural dynamic analysis concerns the behavior of a structure at "resonance." The natural frequency of vibration of a structure --- whether a wood-frame house or a radio tower --- corresponds to that structure's resonant frequency.
		It illustrates the effects of different frequencies of vibration on four different "structures." Each structure has the same mass at the top and the same size (diameter) rod supporting the mass.
		Note that the displacement of the table associated with the hydraulic actuator frequency of motion is very small and is hardly noticeable.
	timber.ce.wsu.edu /supplements/seismic/frequency.htm (238 words)

	Schumann Resonances
		The fundamental frequency of the Schumann resonance is roughly the fundamental frequency of a spherical shell whose inside boundary is the surface of the Earth and whose outside boundary is the ionosphere, acting as a spherical shell electromagnetic waveguide cavity.
		In other words, the natural frequency of the Earth at the boundary of the inner core is about 40 cycles/sec, which is at the upper end of the range of frequencies measured for the Schumann resonances: 7.8, 14, 20, 26, 33, 39 and 45 Hertz.
		The natural frequencies of the Human Brain are: Beta waves (14 to 30 Hz), Alpha waves (8 to 13 Hz), Theta waves (4 to 7 Hz), and Delta waves (1 to 3 Hz).
	www.valdostamuseum.org /hamsmith/Schumann.html (1404 words)

	Results
		To increase the natural frequency to its theoretical value of 66.3 Hz, the rocket holder was discarded to decrease the mass being applied on to the beam.
		The spike at 60 Hz and 68 Hz are induced by noise and the natural frequency, respectively.
		Using equation (5), the cutoff frequency was used as the natural frequency, ω, and assuming the damping ratio to not have much contribution, the error percentage was calculated to be 45.4%.This error, once again, is believed to be associated to the disconnection between the strain gage and aluminum beam.
	www2.hawaii.edu /~bethyama/results.html (1296 words)

	Vibration Control & Noise Control Solutions
		Natural Frequency is the frequency of vibration that will occur if a system is disturbed from its normal position and allowed to vibrate freely.
		The forcing frequency is 30 Hz and 80% isolation, or a transmissibility of.20, is desired.
		Using the previous example, where the forcing frequency is 30 Hz and 80% isolation is desired: Draw a horizontal line across Figure 8 located at 30 Hz on the forcing frequency axis to the intersection of the 80% isolation line.
	www.novibes.com /vibration/techdata/technica.asp (1522 words)

	Chuck's Chimes (Site not responding. Last check: 2007-10-30)
		Note the natural frequency does not depend on the hardness, temper, surface finish, or any other material property of the tube beside the modulus of elasticity and density.
		At a length/diameter ratio the 2nd natural frequency of the air column crosses the the 1st natural frequency for the tube.
		The tube was tuned to where the fourth natural frequency of the tube crosses the fifth natural frequency of the air column.
	mysite.verizon.net /cllsj/windchimes/home.htm (2503 words)

	The Physics Classroom
		So the natural frequency of a wind instrument such as the trombone is dependent upon the length of the air column of the instrument.
		There were a variety of classroom demonstrations (some of which were phun and some of which were corny) which illustrated the idea of natural frequencies and their modification.
		The actual frequency is dependent upon the properties of the material the object is made of (this effects the speed of the wave) and the length of the material (this effects the wavelength of the wave).
	www.physicsclassroom.com /Class/sound/U11L4a.html (1336 words)

	Modal Analysis (Experiment)
		It was shown, using experimental methods such as the frequency sweep and impact testing, that there exists a natural frequency and a corresponding mode shape for each single DOF subsystem.
		It is shown that the peak of the frequency domain of each figure occurs at the natural frequency of the respective mass.
		The frequencies would be the same at both locations, keeping in mind that the natural frequency depends on the mass and the spring stiffness only.
	www.msu.edu /~muhannad/modal_analysis.html (1901 words)

	How do you determine the natural frequency of a solid?
		All the different reasonanct frequencies of different materials are tabulated and the material the building is made out of will determine its reasonant frequency.
		The natural frequencies of something like a solid rod can be determined when the length, Young's modulus for the material and the mass density and, for more complicated systems (such as a pipe, building etc.) the structure.
		Frequencies for this degree of freedom are multiples of a fundamental.
	www.physicsforums.com /showthread.php?t=126109 (772 words)

	Z Microsystems - Hot News - Using the Octave Rule to Predict and Design for Vibration Robustness
		In turn, the plate is attached to the chassis so that the plate's natural frequency is twice or half that of the chassis' input.
		This first harmonic, or natural frequency, is twice the frequency of the input, and hence it has the musical term "octave" (where an octave represents tones eight notes apart and frequency multiples of two).
		This is why the natural frequency is typically the most damaging of the resonant frequencies.
	www.zmicro.com /hot-news/article/16 (1541 words)

	Natural Frequency
		There were a variety of classroom demonstrations (some of which are fun and some of which are corny) which illustrate the idea of natural frequencies and their modification.
		This process of stick-slip friction occurring at a high frequency is sufficient to set the molecules of the glass into vibration at its natural frequency.
		The actual frequency is dependent upon the properties of the material the object is made of (this affects the speed of the wave) and the length of the material (this effects the wavelength of the wave).
	www.glenbrook.k12.il.us /gbssci/phys/Class/sound/u11l4a.html (1443 words)

	What is light
		The natural frequency of the most outer orbital electrons will be in micro wave frequency region and a substance in a very cold temperature (a few Kelvins)emits microwaves.
		This is because, the natural frequencies of the orbital electrons in the atoms of that surface, including in all the frequency in the visible region.
		The natural frequency of orbital electron of the hydrogen atom in' n1'energy level is in ultraviolet region (Lyman series) and a hydrogen atom emits ultraviolet ray in 'n1'orbital exited state.
	www.geocities.com /newideasfromtelewise/prakasham6.htm (4393 words)

	BAIN: The Overtone/Harmonic Series (Site not responding. Last check: 2007-10-30)
		For example, the interval whose frequency ratio is 6:4, should be expressed using the ratio 3:2.
		So the natural interval frequency ratio for that interval can be determined by using the frequency multiple numbers between the staves, in this case 3:2.
		The octave, or interval whose frequency ratio is 2:1, is clearly too large an intervallic distance to be melodically expressive.
	www.music.sc.edu /fs/bain/atmi98/examples/os (2028 words)

	Accelerometer Principles- Developer Zone - National Instruments
		The parameters, natural frequency, and damping coefficient in Equation (5.28) have a profound effect on the application of accelerometers.
		The effect of natural frequency and damping on the behavior of spring-mass accelerometers is best described in terms of an applied vibration.
		Generally, accelerometers are not used near the resonance at their natural frequency because of high nonlinearities in output.
	zone.ni.com /devzone/cda/ph/p/id/12 (1210 words)

	Article - Earth Breathing
		Michael Hutchison states in his book "Mega Brain Power" The 7.83 Hz frequency has been found to be one of those "window frequencies" that appear to have a wide range of beneficial effects on human beings ranging from reports of enhanced healing to accelerated learning.
		When a biological system vibrates at this frequency, it can be said to be in a state of resonance or attunement with the planet's own magnetic frequency....
		If we take on board that the natural frequency is gradually being drowned out whilst our biological systems are still tuned into that frequency, then we must look for ways in which we can tune ourselves back into that frequency.
	www.lightnet.co.uk /innerharmony/techniques/earthbreathe.htm (1047 words)

	Mechanical Design Guidelines for Springs (Site not responding. Last check: 2007-10-30)
		The designers must ensure that springs are operated well under their first natural frequency at maximum engine speed, or they risk damage to the pistons because the springs may not return the valves in time.
		To find the natural frequencies for the rod, we look at where the change in length of the rod blows up.
		We can express the natural frequency for the spring in terms of its geometry and shear modulus (instead of its overall stiffness k and its mass).
	www.efunda.com /DesignStandards/springs/spring_frequency.cfm (537 words)

	Introduction to Experiment 2:Vibrations
		Measure the dimensions of the beam for use in calculation of the theoretical natural frequency.
		In this test, the natural frequency and damping of the bar’s free response is investigated.
		Calculate the theoretical natural frequency of the beam for the different materials and end masses used, and compare to the simulation data.
	www.ecs.syr.edu /faculty/glauser/mae415/vibesLab/goodVibesExp.html (2336 words)

	Multiple Frequency Ultrasonic Cleaners
		Low frequency ultrasonic cleaners produce cleaning action which is more powerful, but less evenly distributed in the cleaning tank, leading to "hot spots" of activity which may lead to inconsistent cleaning results, and even damage to highly polished aluminum parts.
		Outside of this natural frequency, the "rattle" is not produced, and ultrasonic energy is drastically reduced as a result.
		The frequency of the transducer is determined by its size and mass.
	www.zenith-ultrasonics.com /crossfire.htm (1229 words)

	Feature - Chatter Theory Fundamentals
		As the excitation frequency increases, so does the amplitude of the displacement, up to the "resonance." At resonance, the frequency of the excitation force matches the natural frequency.
		Large stable gaps occur at spindle speeds where the rotational frequency of the tool or workpiece is equal to the dominant natural frequency of the system.
		The indisputable concept is that "Spindle speed and chatter frequency are related." Select a spindle speed so that the tooth passing frequency or some multiple of the tooth passing frequency is equal to the chatter frequency.
	www.mmsonline.com /articles/0300sup_theory.html (1662 words)

	AERADE
		The natural frequencies of such multi-span structures occur in groups, the number of frequencies in each group being equal to the number of spans.
		ESDU 73013 gives curves of the fundamental natural frequency of initially unstressed rectangular plates in a panel with flexible stiffeners (not necessarily of the same material as the skin).
		ESDU 75030 gives comprehensive curves that enable the natural frequencies to be calculated for the first few modes of vibration of plates having any combination (symmetric or otherwise) of edge conditions from free, simply-supported and clamped.
	aerade.cranfield.ac.uk /subject-listing/esdu/ES49.html (1290 words)

	\| What's This All About ? \| Natural Frequency
		The aim of the Natural Frequency Journal is to provide a useful resource and act as a forum for anyone interested in energy efficient architecture and sustainable building design.
		If neither of these options are what you are after, then you will need to use the Contact page to get in touch with us -- but please understand that, because of the large amounts of mail we receive, it may take some time to hear back from us.
		Natural Frequency is protected by copyright which is shared jointly between the journal itself and its contributing authors.
	naturalfrequency.com /about (386 words)

	Free Response: Multiple Stories (Site not responding. Last check: 2007-10-30)
		The natural frequencies for this structure are approximately
		You can use the frequency calculator at right to input different values of mass, stiffness, and damping and find out what the model building's natural frequencies would be in that case.
		If we were to apply an initial set of displacements that was proportional to one of the mode-shape vectors, then the free response of the structure would occur at only that mode's natural frequency.
	www.shodor.org /~reneeg/weave/module1/node6a.html (510 words)

	\| Frequently Asked Questions & Answers \| Natural Frequency
		Natural Frequency is protected by copyright which is shared between the journal and its contributing authors.
		Natural Frequency Journal naturalfrequency.com ISSN: 1833-7570, Issue No. 17, 24 May 2005.
		However the team at Square One (who publish Natural Frequency) may be able to help you.
	naturalfrequency.com /faq (436 words)

	Shortening a guitar string to one-third its initial length will change its natural frequency by what factor?
		Given f is the lowest natural frequency of the string, 2f, 3f, 4f, etc. are also natural resonant frequencies of the string, and these are called the "harmonics".
		The natural frequency of a string can be found by looking for a sinusoidal solution where the nodes coincide with the fixed ends of the string.
		Since length and frequency are clearly inversely proportional, if the length is shortened to one-third its initial length, the frequency will increase to three times its initial value.
	www.physlink.com /education/AskExperts/ae632.cfm (309 words)

	How and Why to Measure the Natural Frequencies of Fan Component Parts (Site not responding. Last check: 2007-10-30)
		Component parts of an industrial fan — such as the shroud (rim), webplate (center disk), or impeller blade — have a natural frequency of vibration, which is based on their geometry, material of construction, and points of connection with other components.
		In the third mode at a frequency of 372 Hz, there were two nodes, one at the base of the blade and one just beyond the transition point between the thicker and thinner sections.
		A blade redesign with a stiffer cross section raised the natural frequency of the primary mode to 152 Hz and solved the problem.
	cementamericas.com /mag/cement_why_measure_natural (1192 words)

	Statistics Training That Works With Our Innate Ability To Assess The Likelihood Of Events Can Help Doctors And Patients ...
		Still, the authors predicted that the latter approach would be easier for people to learn because it taps a natural ability to count the observable, without having to use symbolic abstraction.
		Previous research has shown that people calculate the odds of any given event more easily and accurately using natural frequencies, which the authors say represents information in a way that is attuned to our "cognitive algorithms" for reasoning with certain kinds of data.
		For example, jurors must evaluate a greater number of statistical averages and frequencies presented as evidence, and citizens in a growing number of democracies must intelligently evaluate the kinds of information that their governments make public.
	www.apa.org /releases/statistics.html (758 words)

	Tremor: Boss Model
		If the frequency of this oscillation is close to the natural frequency of the building, resonance may cause severe damage, The BOSS model allows students to observe the phenomenon of resonance.
		Perform an experiment to establish the relationship between the height of a structure and its natural frequency.
		Plot height versus natural frequency on the graph provided, (Students should come up with a hyperbola, a curve representing an inverse relationship in which, as the the height of the structure increases, its natural frequency decreases.)
	tremor.nmt.edu /activities/boss_model/bosmodel.htm (980 words)

	Alberta PhysicsSource - eLab - Mechanical Resonance
		If energy is added at the right time, "in tune" with the natural frequency (mechanical resonance), the swing will go higher and higher.
		But if the energy is added "out of tune" with the natural frequency, it will result in the swing losing height to their swing.
		In regard to part 1, calculate the frequency of vibration for all of your trials.
	www.scienceman.com /physics/pgs/2003_per_elab_14.html (1199 words)

	natural frequency definition - Dictionary - MSN Encarta
		natural frequency definition - Dictionary - MSN Encarta
		Search for "natural frequency" in all of MSN Encarta
		frequency at which free system vibrates: the frequency at which a system that has been moved from its resting position will oscillate about the position if there are no disturbing forces
	encarta.msn.com /dictionary_561532075/natural_frequency.html (86 words)

	IDEERS Resistant Buildings - Vibrating Buildings - Natural Vibration - The Natural Frequency of a Building
		The natural frequencies of vibration of a building depend on its mass and its stiffness (or how flexible it is).
		The natural frequency for each mode of vibration follows this rule:
		Taller buildings tend to be more flexible, so they tend to have lower natural frequencies compared to shorter buildings.
	www.ideers.bris.ac.uk /resistant/vibrating_build_natfreq.html (123 words)

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