# What is Attenuation: Definition and 133 Discussions

In physics, attenuation or, in some contexts, extinction is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates.
Hearing protectors help reduce acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs).
In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field.

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1. ### B Log relationship between thickness of material and sound absorbed?

So I have done an experiment on the amount of sound energy absorbed based on thickness of pvc foam, and found a logarithmic relationship between the two. I've used the frequency-dependent acoustic attenuation power law, which is derived from stokes' law. Frequency-dependent acoustic attenuation...
2. ### Sound absorption/Acoustuic attenuation coefficeint (α(ω)) of PVC foam?

I am currently doing a physics experiment to find the frequency-dependent attenuation coefficient (α(ω) )of pvc foam, are there any verified/reliable sources that show the attenuation coefficient α(ω) of pvc foam or materials in general? Best I found is this...
3. ### I How does EM wave geometrical attenuation affect atomic absorption?

Let's say we have a point source of an EM wave in a vacuum of total energy E, and an absorber atom at some distance from this source, whose first excited state is at the energy B, with B < or = E. The energy of the wave is constant as a whole, but at each point around the source the energy...
4. ### Microwave Oven door attenuation in dB?

I recently made a repair to the door switches/bracket on our microwave oven (MWO). All is well, but later, after reinstalling a trim piece and checking the fit, I noticed that with the door closed and latched, that there was a bit of play (1/8"?) - I could push the door a bit further closed, and...
5. ### I Incident electric field attenuation near a metallic plate

Hello everybody, I was visualizing the electric field radiation pattern of an antenna in a 3D EM simulation software (CST), and to see it with my eyes made me realize something I probably heard during my studies but forgot. What is the phenomenon behind what you can see below, which is the...
6. ### Calculating attenuation necessary to reduce number of photons

Hi there. I am attempting to do calculations for my own project, the question being what is the attenuation necessary to reduce the number of photons in a beam to single-photon levels. N approximately 1 or 2. The laser in question is a 650nm 5mW laser. I have solved the energy per photon...
7. ### Attenuation and Phase constant values in wave equation

Regarding wave equation we are faced with this form $$\nabla^2 \vec{E}=j\omega \mu \sigma \vec{E}-j\omega \mu\varepsilon \vec{E}=\gamma ^2\vec{E}$$ where $$\gamma ^2=j\omega \mu \sigma -j\omega \mu\varepsilon$$ $$\gamma =\alpha +j\beta$$ where alpha and beta are attenuation and phase...
8. ### Why smooth spherical waves with attenuation are only possible in 3-D

Hi all, My question is about the attenuation and delay terms in part (1). what are attenuation and delay terms describing in physical phenomenon? thank you. What do "attenuation" and "delay" mean in terms of real-life physical phenomena? Consider the wave equation for spherical waves in...
9. ### Automatic TV attenuation with thumb drive....Possible?

Greetings from Tennessee. I am not an EE but I like to tinker. So you are watching TV and the commercial comes and all of a sudden you are getting blasted out of your recliner. Also when I'm watching Andy Griffith on Amazon prime? Everything is going along fine and then they play some music and...
10. ### How does valve size affect water heater pressure loss?

There are 2 kinds of home instant bathroom water heater. The multipoint and single point (or shower heater). The latter is one where the unit is connected directly to the shower head. In the multipoint, its located a distant away and it serves multi points like sink and bath. What would happen...
11. ### MATLAB How can attenuation be removed using SCIPY or MATLAB?

Dear Sirs, I have a signal which has an attenuation of 20dB per decade, how do I remove this attenuation using SCIPY? Alternatively how to do it in MATLAB if there are no SCIPY users here? I'm a SCIPY/MATLAB novice fyg. Thank you for your kind assistance Abim
12. ### What is the optimal thickness for a Faraday cage to attenuate radio signals?

Greetings, I have a question regarding the attenuation properties of Faraday cages. More specifically, I'm looking for a generalization I can use to better understand how thick they should be for a given frequency. I did a small experiment by taking a small enclosed aluminum box and placed an...
13. ### What is the attenuation below cut-off frequency for TE10?

It is not useful to talk about the attenuation below cut-off frequency, but I have this doubt about what happens to the wave below cut off for an electric conductor. As we know if we derive the propagation constant, it becomes imaginary saying that there should not be any wave propagating in the...
14. ### Attenuation Coefficient in an optical fibre

Homework Statement In a particular fibre, the attenuation coefficient for Rayleigh scattering is measured to be 0.30 dB/km at 1.20 μm. (a) How large would it be expected to be at 0.80 μm? (b) Ignoring other sources of attenuation, if a signal of a certain initial power was sent over a...
15. ### Solving for Attenuation Constant with Power Relations

Hello. In fields and waves and transmission lines We have a attenuation constant formula with power relations: 1- Alpha = 1/2R0(R+G|Z0|^2) 2-Also we can calculate attenuation constant from these : Z0= radical[(R+jwL) / (G+jwc)] gamma = radical[(R+jwL)(G+jwc)] I want show alpha from 1...
16. ### How Does Lead Attenuate 0.5 MeV Photons Over 1.3 cm?

Homework Statement Calculate the fraction of photons absorbed from an attenuated beam of 0.5 MeV photons after it has gone through 1.3 cm of lead? The linear attenuation coefficient of lead for 0.5 MeV photons is 0.5 cm-1. Why is lead a good choice as a material for shielding? Homework...
17. ### B Signal Attenuation (capacitive pickup)

We have a question we cannot understand… We are university students working on a pet project, we are trying to pick up an electrical current passing through a conductor via a capacitive sensor (i.e. attached to a charge amplifier with filters) that is not in direct contact with the circuit...
18. ### Fibre attenuation with absoring cladding

Homework Statement Given a single mode fibre with non-absorbing core and absorbing cladding where the power propagating in the fundamental mode is split 70%:30% between core and cladding, calculate overall attenuation of the mode along the fibre in dB/km at 1550nm source wavelength where the...
19. ### I Mass Attenuation coefficient greater than 1

Hello everyone, I don't seem to understand why mass Attenuation coefficient is greater than 1 at low energies where photoelectric effect is dominant. 5.2 cm^2 /g at water for 10 kev incident photons. Since it is the probability to interact per g of water how can it be greater than 1? I...
20. ### I Linear attenuation coefficient

Is linear attenuation coefficient a constant for a given material or will it depend on the thickness of the material?
21. ### Linear attenuation coefficient for gamma ray attenuation

Homework Statement I have data for the count rate (of gamma rays) against the thickness of various materials (Al, Pb, Fe etc...). I want to work out the linear attenuation coefficient. Can I do this by plotting the natural log of count rate against thickness? I don't have values for...
22. D

### A Helmholtz Resonator: attenuation vs. amplification

Hello guys, I read the other threads about HR, resonances and so on, but I couldn't find a clear explanation of what the practical implications of using a HR are. From one side, HR is described as a "reactive element", used in several contexts to attenuate a specific noise by means of...
23. ### Does attenuation affect subsequent interference?

Consider a 95% / 5% beam splitter. The 95% output is attenuated in a lossy medium until its intensity is equal to the 5% output. If we now get these two beams to interfere, would the visibility be as good as the usual 50% / 50% case, or would there be some kind of added randomness that would...
24. I

### How to calculate attenuation for optical fiber bundle?

Hi, If I understood it correctly, the coefficient of attenuation for a single optical fiber, is alpha = (10/L)*log(P(0)/P(L)). Assuming if I knew the properties of the optical fiber and the amount of optical fiber in the bundle, then the total attenuation for the bundle is approximately number...

Homework Statement http://imgur.com/qBXvrGz Above is a sketch of the circuit, a two stage symmetrical attenuator consisting of two symmetrical T attenuator pads connected in cascade, with the values that I have worked out for the resistors. The reduction is 15dB in the first stage, and 8dB in...
26. ### Filter Performance Assessment Using Basic Equipment: A Practical Guide

Hi, Say I have a design for a filter, is there a method of bench-marking it's attenuation over a variety of loads and types of harmonics? (or even common and differential noises) For instance, say I wanted to compare a filter to an LC filter or a π filter, how does one evaluate how much better...
27. ### Relation of attenuation and swamping

Homework Statement Question: If the attenuation between Earth and satellite is 190dB, with reference to attenuation explain why there should be a difference between uplink and downlink? (I am a senior high school student so I haven't learned in too much depth) The Attempt at a Solution My...
28. ### I Attenuation: Definition, Calculations & Examples

If I'm being asked to calculate the attenuation of a certain type of radiation, what does that actually mean? Is ##\frac{I}{I_0}## the attenuation of the radiation? I'm just confused between things like attenuation and the attenuation coefficient and attenuation length, I think. So what is the...
29. ### Relative Humidity (RH) affecting atmospheric attenuation of light?

Ok, so I have another question that online searches have not been able to produce. Everything I've seen online references sound waves, or RF signals, or electromagnetic waves. I know that the reason we can view sunsets and sunrises safely is because of atmospheric attenuation - the amount of...
30. ### I Difference between absorption and scattering cross sections

Hi. I'm trying to model the attenuation (extinction) of a weak laser through a gas sample using the Beer-Lambert law. I've found that the attenuation cross section can be written as the sum of both a scattering and absorption cross section, however I'm having difficulty finding a source that...
31. ### A Does increasing photon flux density increase attenuation?

follow up from responses in old thread. https://www.physicsforums.com/threads/why-does-attenuation-coefficient-decrease-with-increased-energy.569981/ I have seen in my experiment using a saline media ( some oxygen bubbles) that an increase in Incident PFD is showing an slight increase in the...
32. ### B How does attenuation happen? Very confused

How can light flux decrease after traveling in a medium without scattering it? Does attenuation mean scattering? Also in Infrared spectroscopy, why does the intensity of light decrease when the molecule is vibrating in resonant frequency? Does the electron produce an E field opposite to the...
33. ### B Can we detect ancient EMR attenuation from before the recombination epoch?

My (layman) understanding of CMBR is that it's the oldest observable EMR since the recombination epoch, with a peak wavelength of 1.063 mm. Does it make sense that the EMR from before this time would have an exponentially longer (though still possible to detect) wavelength?
34. ### Gamma-Ray Attenuation in Matter

Homework Statement Hi, I am trying to solve for the cross section for a gamma ray energy. The element I am using is Europium and the energy peak is 244.7 keV. From the slope of the graph I was able to determine the mass attenuation coefficient to be 8*10^-5 m^2/kg Homework Equations σ=(μ*A) /...
35. ### Energy partitioning (Attenuation)

Homework Statement A seismic wave travel from surface, is reflected at the fifth of a series of horizontal interfaces. Each has a reflection coefficient "R" of 0.15. What is the total attenuation in amplitude caused by energy partitioning at all encountered interfaces, when the wave returns to...
36. ### Find an expression for the attenuation from the eqn given

Having a big issue working through this problem and was wondering if somebody, much smarter than I, could give me a few pointers. Anyway here's the problem: Given that k2=εμω2-iωμσ By writing the wave number as k=kr-iki. Show that ki, which determines attenuation, can be expressed by...
37. ### What is the attenuation factor?

Homework Statement the question has a transformer, the hv side of which is connector to a pot that is said to be an attenuator in the question with attenuation factor = .8? the turns ratio of transformer is 1:1.125. I have to find HV side voltage after the attenuation...i know attenuator...
38. ### A Explaining 'Attenuation' in Water Hammer in Pipelines

Hi Who can explain about 'Attenuation' phenomenon in pipelines when water hammer occurs? I mean how it happens.
39. ### A Attenuation and Packing in hydraulic Transients

Hi 1- How can justify two phenomenon 'Attenuation' and 'Packing' in fluid transients in pipelines? Is it possible to explain and account for those with Newton's third law? 2- Regarding to what Chaudhry says in his book ('Applied Hydraulic Transients', P. 192 of 1979 edition, Chapter 7, Part...
40. ### How does probe attenuation affect input impedance on a scope

I assume the 10X setting to be the most useful with audio work. Comments?? My oscilloscope has 1M ohm input impedance when set at 10X as stated above. What is the likely impedance at 1X ? The manual indicates the above chart is based on the probe being set at 10X. As I am dealing with DC...
41. ### Attenuation and source positioning

Hello, I've been reading about attenuation, and I wonder if there's a way to determine the distance to your source. Forgive my poor writing; I'm new to the topic. I understand that equation for linear attenuation is I = I0e-μx where: I = intensity I0 = initial intensity μ = attenuation...
42. ### Calculate attenuation constant of an aperture

Homework Statement The shielding efficiency of an aperture depends on e−αd, where α is the frequency-dependent attenuation constant of the aperture and d is the thickness of the material (or the cutoff waveguide) at frequencies below cutoff. where ωc=2πfc. Calculate α for an air-vent...
43. ### Estimating loss-limited transmission distance

Homework Statement A high-speed optical data communication system is composed of a transmitter, an unamplified transmission fiber link, and a receiver. The optical transmitter generates a 10-Gb/s non-return-to-zero (NRZ) signal using a 1550-nm laser diode (linewidth=2 MHz) followed by a...
44. ### Why does the mass attenuation coefficient have a negative gradient?

I am currently trying to understand the mass attenuation coefficient (MAC) with regards to photoelectric absorption. Consider this graph: Why does this have a negative gradient? Why does the MAC decrease as the photon energy increases? From what I understand, the MAC is the rate of energy...
45. ### What are the equations to measure attenuation of stress wave

what are the equations to measure attenuation, frequency, amplitude of a stress wave propagation of metal rod or plate which is immersed in water or fluid?
46. ### Ultrasound Attenuation: Why Power Ratio?

Hello, I have a simple physics question. It is about ultrasound attenuation. Why is the attenuation a function of the log of the POWER ratio? i.e. why must it be the ratio of power quantities rather than field quantities? what is the physical basis of this relationship? thank you!
47. ### Understanding propagation loss: What does this output mean?

Hi there! I am currently building a simulation to model the propagation of radio waves in seawater in terms of its propagation loss. I have previously discussed the models I've looked at but have settled on a model which depends primarily on the propagation distance ##r##, the carrier wave...
48. ### Wave frequency and propagation attenuation

In my memory, the wave frequency will decrease because the attenuation in wave propagation, is that true? Can someone please give me some links to prove or disprove it? thanks
49. ### Anyone got Graph for attenuation coefficient gold?

Hello, does anyone have a graph for the attenuation coefficient of Gold (Au) (y-axis) with the respective types of interactions with photons of various energies usually from~10^-3 to 10^4 MV (x-axis) and where the incoherent, photoelectric, compton etc...interactions occur? Doing work on this...
50. ### Determine attenuation of voltage in transmission line

Hello, So I have a circuit where I input a square pulse with a source impedance and load impedance (which are just pure resistors) each of which can be varied and a transmission line circuit connecting them which is made up of resistors, capacitors, inductors in a lumped element model. I set...