What is Frequencies: Definition + 412 Threads

Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as temporal frequency to emphasize the contrast to spatial frequency, and ordinary frequency to emphasize the contrast to angular frequency. Frequency is measured in hertz (Hz) which is equal to one event per second. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example: if a newborn baby's heart beats at a frequency of 120 times a minute (2 hertz), its period, T—the time interval between beats—is half a second (60 seconds divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.

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1. A How does phase of merging sines affect overall periodic tones?

How does angular velocity of merging frequencies affect the overall sound of a periodic tone and to what degree? I know this is an extremely complex matter thus I'm just keeping it very simple, as in sticking with only two to a few, known, pure sins. I'm curious as to how much, and in what...
2. Calculate IC equalizer frequencies and gain

Homework Statement: Calculate frequencies/gain in an AC circuit given capacitance and resistance Relevant Equations: Looking for them :P Hi! I have this diagram: BA3823LS monolithic, five-point stereo graphic equalizer IC is used. Is there any way to calculate the frequencies (hz) that are...
3. Engineering Bode Plot Slope based on frequencies

From 0 to ##10^3## ##\omega## there is a dB gain, from ##10^3## to ##10^5## there is another. Finally from ##10^5## to infinity the slope is constant (0). I know the formula $$dbV= 20log_{10}\frac{V_2}{V_1}$$ can give me the slope but that is in terms of Volts, but I have frequency and the...
4. I Planck’s constant: Why are atom vibration frequencies integers only?

Given the definition of whole numbers as integers, https://www.google.com/search?q=what+is+a+whole+number&rlz=1C1VDKB_en-GB&oq=what+is+a+whole+number&aqs=chrome..69i57j0i512l9.11619j0j15&sourceid=chrome&ie=UTF-8 Is it known why atom vibrations are only at whole numbers ( ref plank’s constant)...
5. B What's the reason microwave oven frequencies are at 2.45 Ghz?

Hi, A little background before my question: I read that microwave oven frequencies are at 2.45 Ghz, or about a 12cm wavelength. Lately, 5G is using frequencies called millimeter waves, and these frequencies can be as high as 40Ghz. So, linguistically to me, it seems as microwave oven waves...
6. B Are magnetic fields generated through radio frequencies?

I seem to hear about huge astronomical events that generate radio waves seem to come from objects with huge magnetic fields, such as neutron stars and black holes. Does that mean magnetic fields only come from the radio end of the spectrum, and not higher frequencies, like IR, UV, X-rays, etc?
7. I Infinite Frequencies & Extraterrestrial Signals: What Are We Missing?

And if there are an infinite amount of frequencies, doesn't that mean that an extraterrestrial civilization could be reaching out without us being able to receive their signals. And even if we did receive their signals, how would we understand their form of communication? What if they...
8. I Interference - two waves of different frequencies - beat velocity

Hello, I'm considering the "beats" phenomena. I have two plane waves in some medium with a refractive index n(ω), one propagates in a z direction and second in a direction making an angle θ with z axis. Waves have frequencies ω1, ω2 (not necessarily equal) and k-vectors k1, k2 (not necessarily...
9. M

A Resonant frequencies of liquid in a cylinder

Hi PF! I have been on and off working on a fluids problem for 2 years. I am SO close but the answer isn't coming out clean. I'll highlight the equations I solve and the technique. If you can help me finish this, I'll not only be incredibly grateful but I'll either thank you in the paper...
10. B White noise frequencies and Audio Speakers

Hi everyone . unfortunately for health reasons I have to give it a try and put a pair of audio speakers in my bedroom to reproduce white noise during sleep. I need to know if the audio speakers I already own are able to reproduce the range of frequencies I need, namely that of rain and sea waves...
11. Mathematically Ramp down a sinewave to 0 or switch frequencies

How do Mathematically Ramp down a sinewave to 0 or switch frequencies without causing a clicking sound? I wrote code to play a sinewave but when I stop the sound I can hear a clicking sound. I tried to slowly ramp down the Amplitude, but that seem to only work for some Combination of...
12. I Behavior of a curved 2D sheet and a curved 1D wire under acoustic wave

Good day. We know how simple objects, such as 1D wires behave when a simple harmonic wave travels along a wire, or two wires knotted togethe.We also know what happens if you excite a circular thin disc with a single frequency. Are there some material I can read on, that considers the effect...
13. I Water Waves Over Obstacles: Higher Frequencies Grow, Not Decay

In general, it seems that higher frequencies of a wave dissipate more than lower frequencies. For sound waves, it explains why you can hear lower pitches from farther away. For a vibrating string or plate, the higher frequencies also dissipate first, with the fundamental fading last. For water...
14. I What happened to the range of frequencies after recombination?

So as the hot plasma of a universe expanded it grew colder and at "recombination" it reached a state where it isn't opaque to em radiation any more unlike dense plasma which is. So we say this is the moment the CMB started. But this got me thinking, after recombination the matter was still some...
15. Frequency Shift Key Modulation: how are the carrier frequencies chosen

Question: For frequency shift key modulation in the binary case, how are the two carrier frequencies chosen? From online reading, I have seen that the carriers are chosen to be different but also with the goal of minimising bandwidth and without any overlaps of the spectra, etc. However, I...
16. Do two light waves with difference frequencies connect when they meet?

for example the blue light wave have frequency of about 450Thz and the yellow wave have frequency of about 508thz (I found this data in the internet) , so if this two wave would get closer to each other we would observe them as green wave which have frequency of 526Thz . so my question is...
17. Changing of frequencies in the Doppler effect

I am trying to figure out why the relativity don't get in the doppler effect, that is, why can't we apply the "galileo transformations" in doppler effect? OBS: i am not saying about doppler effect relativistic (using Lorentz transformation) In another words, i am moving in direction to a source...
18. Fundamental frequencies in a violin string.

Why is this wrong?: That is, why is not f = 4fo? Oh. And my figure 1 can be wrong, because maybe i got confused if the string was open or closed in the boundaries, anyway this change nothing the relations (1)
19. Plotting experimental results on resonant frequencies

These are the questions that I can't figure out how to do. I have been assigned a lab report based on resonating frequencies on a string and am having trouble completing some of the questions in the report. This is what i currently have from the previous steps required. A bit of info...
20. Photon wavelengths and frequencies

Hello guys. I was thinking about solar sails and was wondering if it was possible to instead simply create a sail that is pushed by photons create something that creates an opposite force that pushes off the photons. If you did this in theory would you not be able to double the momentum? An...

22. Electrical frequencies that are NOT harmful to people

Now don't get me wrong. I often compared electroshock therapy to trying to shoot an apple off someone's head, blindfolded, with a flamethrower. But what I want to know is are there electrical conductive frequencies that can travel through the human body without causing damage to any of the...
23. Response of (house) lizards to the sounds of various frequencies

Summary:: Is there any peer-reviewed research that tells how (house) lizards respond to sound of different frequencies? At the very beginning, I must admit that my knowledge in Biology does not run beyond high school books. We are becoming more and more disgusted with these house lizards...
24. What is the frequency of the second harmonic on the A-string in guitar tuning?

We’re tuning a guitar using harmonics, and we produce, on our properly tuned E-string, a frequency of 329.6 Hz when we pluck the first harmonic. The second harmonic, on the A-string, is noticeably higher, producing a beat frequency of 1.5 Hz. What is the frequency produced by the harmonic on the...
25. I Find the natural frequencies of small oscillations

Hi, Given a mechanic-problem, I've linearised a system of two differential equations, which the origin was Lagrange-equations. The system looks like this; $$5r \ddot{\theta} + r \ddot{\phi} + 4g \theta = 0´ \\ 3r \ddot{\theta} + 2r \ddot{\phi} + 3g \phi = 0$$  And I shall find the...
26. How close should frequencies be to show 'beating'?

This is for a standard mass-spring-damper system which is being modeled in MATLAB. I have done some research on the internet and it just says that the frequencies should be close to show the beating phenomenon. Is there a general rule of thumb that I should follow to know how close the...
27. Wavelength to Frequency Relationship in Musical Notes

Hi people, So I've been digging into music theory and want to understand the basic reasons for how it is constructed. I've come across a particular relationship but I can't understand the reason it exists. A quick musical lesson: Imagine you've got a pure musical note: let's say C. From a low...
28. How Can Learning Piano Help Me Understand the Physics of Sound and Music Theory?

Hi there, I am a guitarist and have recently decided to learn the piano as a tool for learning music theory. In digging into music theory I've come into wanting to understand it from the very physics of sound upwards. You'll probably find me on forums discussing sounds theory mostly! I live in...
29. Sizing corner reflectors for frequencies in the audible range

I'm contemplating extending the concept of corner reflectors to wavelengths in the audible spectrum, specifically road noise. I read somewhere that road noise is predominantly between 800 Hz and 1300 Hz. The corresponding wavelengths (at 20°C) are 16.9 inches and 10.4 inches. I read elsewhere...
30. M

A Sessile drop fluid oscillations and frequencies

Hi PF! I'm looking at a sessile drop of water in ambient air. The drop is plucked lightly, inducing surface oscillations. The fundamental frequencies ##\lambda_i## can be computed from spectral theory, and output complex values, say ##\lambda_1 = 2+7i##. Now, I simulate the experiment via CFD...
31. I Find Practical Resonance Frequencies in Linear Differential Equations

Hi all, I would like to know what is the equation upon which I can use to determine the practical resonance frequencies in a system of second order, linear differential equations. First some definitions: What I mean by practical resonance frequencies, is the frequencies that a second order...
32. M

I The fast Fourier transform and droplet frequencies

Hi PF! Suppose we take a drop of fluid and let it sit on a substrate, and then vibrate the substrate. Doing this excites different modes. If someone where to analyze the vibrations, would they take an FFT of the interface, basically reconstructing it from basis functions (harmonics), where the...
33. I Problem with the harmonic oscillator equation for small oscillations

Hey, I solved a problem about a double pendulum and got 2 euler-lagrange equations: 1) x''+y''+g/r*x=0 2) x''+y'' +g/r*y=0 (where x is actually a tetha and y=phi) the '' stand for the 2nd derivation after t, so you can see the basic harmonic oscillator equation with a term x'' or y'' that...
34. I What is the range of natural photon frequencies?

Given that electromagnetic waves transport energy via photons, what is the lowest and highest possible frequency of a photon and what physical phenomena do these relate to? It is clear that the larger the wavelength the lower the energy for a photon. so what are the limits of the wavelength?
35. Is Size 6 the Right Fit for Me? Understanding Mean, Median, and Mode

is the most common size 6 , is my taking right, if not please provide explanation please
36. I Fourier transform, same frequencies, different amplitudes

I understand that the Fourier transform is changing the domain (time/space) to frequency domain and provides the sin waves. I have seen the visualizations of Fourier transform and they are all showing the transform results as the list of frequencies and their amplitude. My question is, what if...
37. I Resonant frequencies of a membrane, dependance on Young's modulus?

Hello, natural frequencies of (circular) membrane are expressed in every textbook as: where is the m-th positive root of the Bessel Function of the first kind of order n. For m=1, n=0: ξmn = 2,405. represents the radius of membrane, and is the velocity of wave propagation...
38. Home Brew RF dummy load showing reactance at higher frequencies

I searched for dummy loads and found nothing on point. If there is and I missed it I apologize. If this is not correct section let me know and I will re-post. We need a high power dummy load in the 4kw range. for the amateur hf bands. The oil cooled "cantenna" type are at the most 1.5 kw...
39. A Natural frequencies of simplified tympanic membrane model

I am trying to anallytically determine natural frequencies ƒ of the tympanic membrane. I am using 2D sectorial annulus membrane as a simplified model of tympanic membrane according to following picture The parameters that i want to use are following: THICKNESS = 0,1 mm The natural...
40. Alternatives to creeping contacts for high frequencies

I anticipate immediately that I am not sure if this is the right place to ask my question, in case I had made a mistake I would migrate willingly into the relevant area. I have an RF circuit on small PCB board (about 3x2 cm) that moves along a vertical axis in a measuring probe (it serves...
41. I Why different cutoff frequencies for TE and TM in a medium?

Today in my electro-magnetics class, we were told that the cut-off frequencies of TE and TM waves on a co-axial cable are different. As far as I understand, it says that if there is an electric field with one frequency projected on it and if we know that the problem can be simplified if we see...
42. Resonance between spring and pendulum: Different frequencies

Hi. I have a spring with spring constant 30 N/m and a mass of 0.5 kg. With the mass at the bottom, the spring has the length 58 cm at rest. If I now pull down the mass and release it, it starts with a vertical oscillation, then the spring also starts to swing sideways like a pendulum and the...
43. Can I get different frequencies from He-Ne Laser ?

Hi guys, can I get different frequencies from He-Ne Laser? if Not? why is it used in Infrared spectroscopy?
44. R

How do I stop multiple radio frequencies ....Micro, Infra an

How do I stop multiple radio frequencies ...Micro, Infra and combined frequencies used in a sweep rotation(?? guessing here) ...from any space. Thank you for any advice you can give. Been traveling. For the record I thought...wearing magnets ?? I have some minimal back ground in RF but am a...

46. Frequency of a standing wave based on slope?

<Moderator's note: Moved from a technical forum and thus no template.> I've done an experiment on standing waves on a string. By graphing √T vs λ (where T is tension and λ is wavelength) using the linearized equation √T = (1/√μ) f ⋅ λ, I was able to get this data: μ = .000256 kg/m slope = 1.78...
47. I Use the Dirac Equation to calculate transition frequencies in Hydrogen

I would just like to understand how to use the above Dirac energy equation to calculate (for example) the 1s-2s transition frequency in hydgrogen. Does one substitute n=1, j=0 for 1s energy level and n=2, j=0 for 2s energy level ? From previous reading I understand the mass referred to in the...
48. C

I What is meant by "low frequencies"? (EM skin depth question)

I'm studying conductors, where complex wave number ##K=k+iα## and complex index of refraction ##N=n+iκ## is introduced. My textbook(Fowles Optics) says that for "very low frequencies", skin depth δ is equal to ##δ=\frac{1}{α}=\sqrt{\frac{λ_0}{cπσμ_0}}##. What is "very low frequency"? How much...
49. B Propagation of information/energy at different frequencies

The Sun, mass decreases as energy increases, i.e. 2 x hydrogen = 1 x helium ( less a little bit = a photon ) until it is ultimately swalled up by a black whole, a magnet with strong force, a ball of iron? am I on the right lines ?
50. A pulse of frequencies that start in phase - pulse period?

Hi, I start at 100 MHz have 10 carrier frequencies all starting in phase at t=0 and the carrier frequencies have 25 kHz spacing. So my frequency range is 100-100.25 MHz, with 10 single frequencies equally spaced in this range. They come in phase every 4x10-5 seconds. The equation Frequency = 1...