Questions tagged [frequency-response]

Frequency response is the quantitative measure of the output spectrum of a system or device in response to a stimulus, and is used to characterize the dynamics of the system.

Filter by
Sorted by
Tagged with
71
votes
4answers
187k views

What is meant by a system's “impulse response” and “frequency response?”

Can anyone state the difference between frequency response and impulse response in simple English?
16
votes
3answers
25k views

How poles are related to frequency response

I have recently fallen into fallacy, considering pole s=1 as there is infinite response at frequency 1. Yet, response was only 1. Now, can you derive the frequency response, given the poles? ...
11
votes
3answers
5k views

How to Average Complex Responses (and Justification)?

I am developing software that calculates the response of a system by comparing the FFT of input and output signals. The input and output signals are divided into windows and, for each window, the ...
11
votes
3answers
8k views

How to estimate a transfer function from a magnitude-only frequency response?

Given an arbitrary frequency response, what signal processing methods might exist that could guess, estimate or determine a transfer function (pole and zero constellation) which gives a "reasonably ...
11
votes
1answer
2k views

Approximating the frequency response of a median filter

A median filter is a non-linear and lossy process, so it doesn't have a closed form frequency response as would a FIR filter (say a box filter of the same length) in an LTI system. But how closely ...
10
votes
1answer
833 views

Ultrasonic speaker calibration and emitting calibrated signals

I'm trying to calibrate an ultrasonic speaker with the aim of emitting predictable signals, but alas I keep running into trouble, probably due to my lack of DSP-fu. A little background I want to be ...
8
votes
2answers
388 views

Why are there comb-like hills in a periodogram?

I am playing with the periodogram of MATLAB. I created a simple script to observe how it behaves: ...
8
votes
2answers
281 views

Evaluating loudspeakers

If you don't have a lot of money to spend but you want to estimate the frequency response of different loudspeaker setups what is the best way to do it? I bought a very nice microphone and built a ...
7
votes
1answer
5k views

Plotting the magnitude response of a biquad filter

I've put together a multi-band audio EQ using biquad filters. I'm getting the coefficients using the methods from the RBJ cookbook. Now I want to plot the curve showing the magnitude response. I'm ...
6
votes
3answers
2k views

Sine sweep vs impulse response

What kind of pros and cons does these method for identifying a system have? I seem to have a hard time finding literature discussion in this issue. I am operating on a linear system, or the linear ...
5
votes
2answers
543 views

Is it possible to infer the characteristic curve of a recording device only from (many) recordings?

... with a certain degree of confidence / corridor of accuracy. What do I mean? Case in point: There is the huge archive of digitized Edison wax cylinder recordings. They have annotations, usually ...
5
votes
1answer
323 views

Understanding the $\mathcal Z$-transform

I was studying $\mathcal Z$-transforms and found pretty good material on the topic, though I feel I do not have a proper understanding of the concept. Could someone help me clarify this? I know that ...
5
votes
2answers
260 views

Find the frequency response of a system

I'm trying to find the frequency response $$H(\omega) = Y(\omega)/X(\omega)$$ for this system- the signal equations are given: $$y[n] = v[n - M] - g * v[n]$$ $$v[n] = x[n] + g * v[n - M]$$ I've tried ...
5
votes
6answers
3k views

Design of a digital A-weighting filter with arbitrary sample rate

I want to A-weight a time series with arbitrary sample rate. An analog A-weighting filter is defined exactly by IEC 61672-1. But there's no definition for a digital filter. One method is to use the ...
5
votes
2answers
1k views

Relationship between the Real and Imaginary parts of a LTI causal system

Prelude I am writing an elaborate text on the relationship between the real and imaginary parts of a LTI causal system and how stability, causality and analyticity imposes various constraints on its ...
5
votes
2answers
4k views

Complex impulse response functions?

I think I must have misunderstood something regarding the relation between impulse and frequency responses. I have calculated the Impulse Response Function, IRF, from the Frequency Response Function,...
5
votes
1answer
858 views

Constant Magnitude Chirp across audio band (Parseval's Theorem?)

I want to excite a loudspeaker with a constant magnitude chirp that sweeps across all frequencies in the audio band. I downloaded a test file from this website to start with. I plot the log magnitude ...
5
votes
0answers
382 views

Impulse Response / Frequency response Question [closed]

I have a major question. Please take a look. I have this differential equation (DE): $$ \frac{d^2y(t)}{dt} +\frac{dy(t)}{dt} +4y(t)= \frac{dx(t)}{dt} +2x(t) $$ And I have to find impulse response (...
4
votes
3answers
12k views

For an LTI system, why does the Fourier transform of the impulse response give the frequency response?

I know that for a given system, the Fourier transform of its impulse response gives its frequency response. I want to find where this property comes from, but haven't been able to find if it's a ...
4
votes
5answers
602 views

Can two different impulse responses give the same frequency response?

I have two different impulse response each with different length, is it possible that they have the same frequency response?
4
votes
1answer
1k views

Compensating Loudspeaker frequency response in an audio signal

I have been working on a project in which I was required to work on the audio signals recorded from the loudspeaker kept in front of a filter. So, to simply explain it: $$\boxed{\rm LoudSpeaker} \...
4
votes
1answer
154 views

Guess the frequency response of a filter with little information

I have a processing unit that does a nice EQ filtering on soundfiles. The only thing I can do is : I give the original .wav file, and the processing unit gives me back the filtered .wav. I have no ...
4
votes
1answer
463 views

Impulse Response Question

For the differential equation $$\frac{d^2y(t)}{dt^2}+\frac{3dy(t)}{dt} + 2y = x(t),$$ I was able to find the frequency response as $$H(j\omega)= \frac{1}{-\omega^2+3j\omega+2}.$$ However, I am not ...
4
votes
2answers
1k views

Least-squares digital IIR filter design (with arbitrary responses)

I'm studying the IIR filter design that is described in the book: Algorithms for the constrained design of digital filters with arbitrary phase and magnitude responses. You can get the code at page ...
4
votes
1answer
1k views

What exactly is Savitzky-Golay differentiation filter?

I could understand Savitzky-Golay filter as being smoothing filter, but then there also seems to be Savitzky-Golay differentiation filter, though for some reason, details do not seem to be clear. So ...
4
votes
1answer
389 views

Discrete-time Biquad filter: Relation between peak frequency and pole frequency

This question arose from a discussion in the comments to this question and its answer. The author of that question discussed a discrete-time second order filter described by the following difference ...
4
votes
2answers
267 views

Frequency response of a rolling linear regression

I am looking for a way to characterise the frequency response of the slope from a linear regression. We are exploring the effect of window length of the regression to the magnitude of the slope of the ...
4
votes
1answer
414 views

BPSK modulation under bandlimited channel

I modulated signal using BPSK modulation and I have series of -1 and 1. Now I have to pass these signal from band limited channel that has frequency response of the form $$\frac{s^2}{as^5+bs^4+cs^3+ds^...
4
votes
1answer
2k views

What is the meaning of a Nyquist diagram in a vibration signal

I need to analyze some vibration data from accelerometers (g-Hz) but I don't quite understand the meaning of each component that the registered signal contains. Basically it is Magnitude and Phase. I'...
4
votes
0answers
439 views

Attempting to use the trapezoidal rule to form a difference equation representing a circuit

I have a differential equation that has been proven to be correct. The transfer function obtained by Laplace domain analysis and Matlab freqs match up and all is well. The problem is somewhere in ...
4
votes
0answers
196 views

Digital control: Exercise solution

Can you help me (show me how) to solve the following exercise? For the process with transfer function $G(s)=e^{-2s}/(s+1)$ design a digital controller with sampling time $T_{s} = 1$ that meets the ...
3
votes
2answers
3k views

Finding the frequency response of a filter defined as a Z-domain transfer function

I am software engineer studying DSP on my own. I came across this question in a graduate textbook and am not sure how to proceed. ...
3
votes
3answers
806 views

Berchin's FDLS arbitrary filter design algorithm

I'm trying to use Berchin's FDLS methods (for those that don't know what it is, it's a way to design arbitrary magnitude and phase of an IIR Eq) I tried different things but neither gave me what i ...
3
votes
2answers
198 views

Frequency response of system with feedback and feedforward co-efficients?

For seismological application, I am playing with an elliptical filter, and once I have both sets of feedback and feedforward co-efficients, how do I make it so that I can plot the frequency response ...
3
votes
1answer
583 views

Frequency response of Low pass filter and High pass filter

The transfer function of a Low pass filter is H(w). From this I want to develop a high Pass filter. I read in DSP by Proakis, Sec 4.5, that the high pass filter can be obtained by translating H(w) by ...
3
votes
1answer
3k views

Difference between $\tt freqz()$ and $\tt plot(abs(fft()))$ in MATLAB

I've plotted the response of a high-pass filter x=[1 -1]; freqz(x) gave me where as the magnitude plot for the ...
3
votes
3answers
919 views

Frequency response equivalent to characterise transient response (to sinusoidal inputs)?

I am interested in characterising the time-dependent response of a system to a sinusoidal input. The steady state response of the system is also sinusoidal, however I wonder if there is a standard ...
3
votes
1answer
755 views

Measuring frequency response range of piezoelectric disc

How can I measure the frequency response range of a piezoelectric disc below. I don't have an oscilloscope but I do know how to program in matlab / octave I was thinking of creating a swept signal in ...
3
votes
1answer
271 views

Frequency response of $\mathrm{sinc}[n]$

In this image the frequency response of a discrete time filter given as $h[n]$. Can someone explain how the magnitude of the frequency response is found ?
3
votes
2answers
935 views

The frequency response function (FRF) fails to detect the antiresonance of a system

I am trying to identify a vibrational systems by computing the frequency response function (FRF) of the system when a chirp signal is applied to its input. After comparing the FRF computed and the ...
3
votes
1answer
78 views

Given a plot of both the magnitude $|H(\omega)|$ and its angle, How can you find the $H(\omega)$?

I'm specifically trying to use an inverse Fourier Transform to find $h(t)$, but I'm finding it difficult to get $H(\omega)$ in the first place. I'm under the impression from my textbook that $H(\...
3
votes
2answers
1k views

FFT and frequency response

There is a system (consisting of several LTI analogue filters) whose input and output signals are being recorded at $20 \ \mathrm{kHz}$ (the sampling period is in the range of 10 times the system's ...
3
votes
2answers
90 views

Multiple filters or not?

I'm processing audio signal sampled at 44.1 kHz. After some other processing, I need to filter the signal between ~5-50 Hz. Achieving this for a signal with such a high sampling frequency appears to ...
3
votes
1answer
932 views

Amplitude vs Frequency Response

Consider the simple first-order low pass filter, described by $\tau \frac{d \mathcal{O}}{dt} + \mathcal{O}(t)=\mathcal{I}(t)$ Considered as a linear system (ie $\mathcal{L} \mathcal{O} = \mathcal{I}$...
3
votes
1answer
192 views

Plotting the frequency response of a FIR filter

I am trying to figure out the mechanics of plotting the frequency response of a FIR filter. For example, I have used an algorithm (Parks-McClellan), to generate a low pass FIR filter with an even ...
3
votes
0answers
5k views

1/3 octave spectra from fft

I have got a signal in frequency domain. This is a frequency response function from software, so I can do nothing about it and have to leave it in frequency domain. I want to transfer the data to 1/3 ...
3
votes
0answers
261 views

Hints and helps to implement an accurate wavelet packet transfrom

I want to implement a Time-Freqency analysis by wavelet packets. I don't know what level and sampling rate should I use. I've tried different value for level(3,4,5,6,). but I couldn't get an accurate ...
2
votes
2answers
556 views

Design a linear-phase FIR filter approximating the magnitude of a given IIR filter

I have a biquad IIR filter from which I want to get a linear-phase FIR. I saw that related question but the OP does not care much about phase. I have troubles getting the exact same magnitude curve ...
2
votes
2answers
3k views

How frequency response related to a transfer function

Can anyone explain how frequency response related to a transfer function?
2
votes
2answers
242 views

Phase function of filter

I have a filter with the transfer function $$H(z) = 1 - 2z^{-2} + z^{-4}.$$ The task is to find the phase function $\theta (\omega).$ My attempt is to start by expressing the frequency response \...