Talk:Frequency response

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[edit] Audio frequency response

Frequency response is often used to describe the performance of audio-related devices, however, it is also often used to describe the performance of, for example, coaxial cables, category cables, video switchers, wireless communications. All of those examples operate well into the gigahertz range. Subsonic examples could include earthquakes, electroencephalography (brain waves). This article should touch on all major disciplines where a frequency response measurement is often used. Snottywong 14:37, 13 September 2007 (UTC)

I agree with you. Perhaps you'll want to add to or reorganize my changes. Binksternet 16:17, 13 September 2007 (UTC)

[edit] Phase Response

This article implies that the phase response is part of the frequency response. While they are often seen next to each other in specs and whatnot, I think the frequency response and the phase response are two different things. Phase shouldn't be mentioned in this article.Snottywong 14:22, 13 September 2007 (UTC)

[edit] Comments from 2004-2005

Shouldn't this page be merged with transfer function? Jorge Stolfi 03:20, 25 Mar 2004 (UTC)

No. The two are not the same thing at all. Graham 05:08, 25 Mar 2004 (UTC)

Ok, but then the definition of "frequency response" needs to be made more precise.
As it is, one could argue that the two are synonymous, and that the phrase "X has a frequency response of 20Hz - 20,000Hz ±1dB" is only an informal way of saying "the frequency response (=transfer function) of X has constant modulus, ±1dB, between 20Hz and 20,000Hz".
So, assuming that the quoted example is indeed pretty much the definition, what about this rewording:

"The frequency response of a signal processing system is the range of frequencies over which the system's gain is constant, within a prescribed tolerance. For example, a high-fidelity audio amplifier may be said to have a frequency response of 20Hz - 20,000Hz ±1dB, which tells you that the system responds equally to all frequencies within that range and within the limits quoted.

It is commonly used in connection with electronic amplifiers and similar systems, particularly in relation to audio signals. As such it is not a measure that is very useful in terms of the quality of reproduction, only that it fulfils the basic requirements needed for it.

Jorge Stolfi 00:17, 26 Mar 2004 (UTC)

I accept the rewording is something of an improvement, so feel free to amend the article. However, you are confused, I think, as to what transfer function means. The rewording doesn't mention this, so it doesn't matter in this context. Transfer function has a much wider meaning than frequency response, and can be applied to almost any system that has an input and an output. In respect of an amplifier, the transfer function is more to do with its linearity (i.e. distortion) than frequency response, though I suppose the case could be made for talking about the transfer function as it varies with frequency. Knowing this, one could extract the frequency response from it. TF is a complex, multi-dimensional aspect of a system, the FR is merely one limited "view" of it, which ignores many other parameters. Hope this helps! Graham 01:57, 26 Mar 2004 (UTC)

someone needs to add how the frequency response is related to the Fourier transform, eigenfunctions, and LTI system theory.

Yeah, right now the article doesn't address frequency response as I learned it at all. Namely if you've got some system with frequency response H(ω), input x(t) and output y(t) then you know that

$\hat{y}(\omega) = H(\omega) \hat{x}(\omega)$

where the hats indicate Fourier transforms, and therefore the phase of H(ω) is important, contrary to what the article currently says.

It does say that you can find the frequency response by using a Dirac delta function, which is the only reason I didn't doubt the terminology I learned in my very few engineering classes. So if x(t) = δ(t)

$\hat{x}(t) = \frac{1}{\sqrt{2 \pi}}$