# What is Cancelling: Definition and 36 Discussions

Noise-cancelling headphones are headphones that reduce unwanted ambient sounds using active noise control. This is distinct from passive headphones which, if they reduce ambient sounds at all, use techniques such as soundproofing.
Noise cancellation makes it possible to listen to audio content without raising the volume excessively. It can also help a passenger sleep in a noisy vehicle such as an airliner. In the aviation environment, noise-cancelling headphones increase the signal-to-noise ratio significantly more than passive noise attenuating headphones or no headphones, making hearing important information such as safety announcements easier. Noise-cancelling headphones can improve listening enough to completely offset the effect of a distracting concurrent activity.

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1. ### I Is g(x) Equal to g(a) If Their Integrals Are Equivalent?

Howdy all, Let's say we have, in general an expression: $$\int f(x) g(x) dx$$ But in through some machinations, we have, for parameter ##a##, $$\int f(x) g(x) dx = \int f(x) g(a) dx$$ ...can we conclude that ## g(x) = g(a) ## ???? Thanks
2. ### Am I overthinking this? (Noise cancelling headphones for airplane noise)

Can I just shift the wave over by 2Pi to get the opposite wave?
3. ### Automotive Cancelling effects on a larger brake rotor

Hello all, I am struggling to find out what exactly makes to have very little advantage in terms of cold stopping distance when you fit larger brakes on a car. Important note, the discussion is only regarding the braking power in the very first stop, before the heat starts to become a problem...
4. ### Strange question about cancelling electric fields

I am curious about the case where two electric or magnetic fields cancel each other out (I'm assuming this is possible). If a charged particle travels through the region where the cancellation exists, I am assuming the particle behaves as if no field exists. Does that area still have electric...
5. ### B Justification for cancelling dx in an integral

In Paul Nahin's book Inside Interesting Integrals, on pg. 113, he writes the following line (actually he wrote a more complicated function inside the integral where I have simply written f(x))... ## \int_0^\phi \frac {d} {dx} f(x) dx =...
6. ### Is this answer incorrect for cancelling waves?

Homework Statement A wave is traveling to the right shown in the first picture. Which wave traveling to the left will momentarily cancel out the original wave moving to the right? Homework Equations There are no equations, this problem is visual The Attempt at a Solution It seems the...
7. C

### I (QED) The initial mass and the correction cancelling out

The prefix is a bit irrelevant This is on renormalisation. How do they cancel out? Isn't it adding? So the mass experimental = m + (c2correction) so how do you cancel out the m and correction? I'm new to this area (just finished watching lectures by Richard Feynman, specifically a 4 lecture...
8. ### Why is the electric field inside the dielectric cancelling?

So, I was studying force between the plates of a capacitor when a dielectric is inserted. Here is my question https://ibb.co/cenvXk Shouldn't it be like this picture below https://ibb.co/kOUsCk So, why is my teacher saying that the electric field inside the dielectric cancelling. So, what...
9. ### How can you negate impact force?

In my science fiction universe, I have a small technology called a 'Kinetic Absorption Module'. It's not mentioned very often, but it's a key component of my supersoldiers' armor. How it works is it acts like a shock absorber, but within a small, one inch long by one and a half inch wide...
10. ### A Can Noise Cancelling Theory Be Used to Send Secret Messages?

Hi, I had kind of a cool idea and was wondering if someone would try and refute it or tell me if it would be possible. So let's say you have three people sitting three metres apart, and you need to deliver a message via sound to person B, who is the person in the middle. Would it be possible...
11. ### Issue with Cancelling ESL for Input Capacitors

I'm trying to set up a DC power supply filter for a 2kW motor controller. I'm trying to set up inductance cancelling for the input capacitor array. When I simulate the coupled T filter in the frequency domain I get what I expect to see. However when I simulate the transient response I'm still...
12. ### How is V1 deduced to be zero in the last step here?

Homework Statement A billiard ball moving at 2 m/s collides (0 degrees) with another of the same weight and at rest, in a perfectly elastic collision. Demonstrate with equations why the balls trade velocities. Homework EquationsThe Attempt at a Solution In the provided explanation, I can...
13. ### Effect of noise cancelling audio equipment

Noise cancelling earbuds/headphones differ from noise isolating earbuds/headphones. Noise isolation just keeps the sound out, whereas noise cancellation actively produces sound in order to "cancel" noise.I understand how this works technologically, however do these sound waves cancel out so that...
14. ### Justification for cancelling terms in limits?

I am confused about the algebraic process of finding a limit. Let us take ##\frac{x^2 -1}{x - 1}##. In trying to find ##\lim_{x\rightarrow 1}\frac{x^2 -1}{x - 1}##we do the following: ##\displaystyle\lim_{x\rightarrow 1}\frac{(x+1)(x-1)}{x - 1}## ##\displaystyle\lim_{x\rightarrow 1}x+1##...
15. ### Solve the Audio Jack Mystery with Nat

Hello everyone :) I came across a strange situation today when I was listening to my music with my headphones on. When I pressed play to a song, the instrumental intro started off fairly normally (although the audio sounded a little "thinner" than usual, as if compressed), and then, when...
16. ### Planar wave expansion cancelling through interference

Hello everyone! In a hypothetical 3D space, with no boundaries around, homogeneous normal conditions, what would happen to the advancement of a planar wave front produced at t=0 with 2cycles in length, λ=3.5m, moving with vector speed "c-arrow=1i-arrow" if an identical planar wave of 2cycles in...
17. ### Cancelling the Signs in Algebra

Homework Statement This is the simplest problem you would ever get. ##\frac{-fu}{s-f}=\frac{fu}{-s+f}## This is true. So the signs can be cancelled.What are the rules for doing that? I guess I was not listening to the teacher when I first learned algebra. The Attempt at a Solution...
18. ### Noise cancelling device, making one

This is an instant idea that I got right after i read an article about noise. Do you think it is possible to make an noise cancelling headphones by using the LM741. Except, i won't be amplifying the signal from the inputs (i can if choose to by just adjusting the varistor) but by using this op...
19. ### Building A noise cancelling program.

Hello, If there is a fixed noise like a faucet running, and I sit in a deskchair at a fixed location in an adjacent room, do you think it would be possible the build a program for either the desktop speaker (also fixed), or another computer somewhere else in the room which would cancel out...
20. ### Electric Fields Cancelling Out?

Homework Statement An example problem I am reading is about the electric field of a uniform ring of charge. I attached the diagram provided in the problem. What confuses me is that the electric field lines in the y-direction cancel out. Wouldn't the fields have to cross, if they were to...
21. ### Cancelling the Earths magnetic field

Homework Statement A researcher would like to perform an experiment in a zero magnetic field, which means that the field of the Earth must be cancelled. Suppose the experiment is done inside a solenoid of diameter 1.0{\rm m} , length 5.0{\rm m} , with a total of 9000 turns of wire. The...
22. ### Understanding Why ln(x) and e Cancel Out

Hi, I have a hard time understanding why ln (x) and e cancel out, when, for example, we have something like: eln(2x+3) I tried an internet search but I did not get any good explanation, just statements of the rule. Could anyone help me please? Thanks!
23. ### What Do Mathematicians Think of Physicists Cancelling dx?

In some places in physics like proving the wave equation,we see that the physicist divides the equation by dx or \partial x or maybe cancels some of them and then says with a smile:You shouldn't tell a mathematician! I want to know the ideas of mathematicians about that and want to know why...
24. ### A questions about Cancelling out brackets.

Hello all, I am new here and I am currently studying IGCSE Math. Hope you can explain something to me. I have what you may think is a basic question... I just wanted to query it. Its to do with cancelling out brackets. so 2x-(x+3) = 2x-x-3 = x-3 I think I...
25. ### Partial Fractions, Method of Cancelling

Homework Statement Expand Using Partial Fractions: f(x) = ( 5x-10 )/ ( (x+1)(x-4) ) Involves Integrating afterwards but I don't think this affects my method.Homework Equations This was a question in my mid semester exam, I got the answer correct but he insists my method is wrong.The Attempt at...
26. ### Cancelling out Power Supply Noise out COMPLETELY

Hi I have a HV (R2) resistor that I want to test for noise. Assuming the 2 low voltage resistors are perfectly stable and HV R1 is also perfectly stable. How could I completely cancel out the noise of the power supply if the bridge was slightly unbalanced? Does any circuit exist that can do this?
27. ### Can Air Compressor Noise be Cancelled Without Affecting Air Flow?

Is it possible to cancel noise from an air compressor while still allowing air flow to keep it cool?
28. ### Cancelling out units in an equation

Hi i have done all the work for this problem calculating viscosity and i come to the last part where i need to manipulate and cancel out units to come to a final solution. The equation works out as viscosity = 0.0042m^2 x 9.8m/s/s x 11,401.4kg/m^3 all divided by 1.034466m/s viscosity is...
29. ### Lagrange multipliers: Variables cancelling out?

Find the maximum and minimum of f(x,y)=y2-x2 with the constraint x2/4 +y2=2. My calculus professor gave us this on his exam and there were no problems like this in the book and I would just like to know how it's done because it's bothering me ha. After doing the partial derivatives I got...
30. ### Teslar watches and other EMF cancelling devices

Are these things for real? I know that most of the crystal pendant crap is fake, but what about teslar watches? Are there actual wristband/necklaces that can cancel, or shield a body from EMF? Thanks.
31. ### Can you cancel differentials in partial derivatives?

often times you will see naive people cancel differentials to obtain whatever it is they want for example : \frac{dx}{dy} \frac{dy}{dz} = \frac{dx}{dz} now i know this isn't rigorous and my question is actually about partials. is there ever an occassion/space/set/etc where i can do...
32. ### Cancelling Confusion with Complex Numbers and De Moivre's Theorem

hi i'm confused at to how my textbook has done the following cancelling :S. hope you can clear things up for me :D thnx context: I am looking at complex numbers and De Moivre's Theorem and its consequences Ill use \oslash as the "arguement". 1. z_{1}z_{2} =...
33. ### Physics Algebra Cancelling Help

Homework Statement I need to know how to cancel terms in the equation Ve = sqrt 2(6.6742 x 10^-11 N m^2 / kg^2 (12.1kg))/0.106780959m Homework Equations Ve = sqrt 2(mu)/r Where r is the distance from the denter of the object to be escaped from, and mu is the Gravitational Constant...
34. ### How difficult is it to cancel an AOL account?

Don't for get to click on the video. http://www.msnbc.msn.com/id/13447232/
35. ### Cancelling Vectors: A=B? Is it Legal?

Do cancelling rules work for vectors? For example, if you had A\vec{x} = B\vec{x} could you cancel out the x's and be left with A = B? Is that legal? edit: A and B are matrices. Does this make a difference?
36. ### Cancelling Squares: Can It Be Done?

Greetings friends, I have come across an argument on cancelling the squares on either side of an equation. For example if the equation is (a-b)^2=(c-b)^2 my argument is that i can cancel the squares by taking the square root of both sides as to get (a-b)=(c-b) and hence a=c. But others says...