# Questions tagged [frequency-spectrum]

The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain.

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### Allan variance plot does not match with the true plot

I am trying to simulate an Inertial Measurement Unit (IMU) by generating sample noisy gyroscope and accelerometer data. Currently I am analyzing the simulated gyroscope( gyro) data. Using the noise ...
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### Detect digitally time stretched audio made back to tape

Can anyone tell me how I might detect and measure a digitally time stretched audio signal (Pro Tools) when subsequently made back onto tape? Could quantization of the signal be detectable on tape and ...
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### removing spikes from spectrum

I am working on 50 samples obtained from time domain signal by FFT. It appears at certain frequencies which are -- according to our experimentalist -- due to some issues with their oscilloscope. What ...
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### Why does FFTPack 5.1 not give the same complex numbers as Matlab's FFT2 command does?

I'm doing FFT2 with FFTPack 5.1 and it's working great. But it does not give the same result as Matlab's FFT2 command. Turning Time domain -> Frequency domain -> Time Domain give the same result ...
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### Comparing results for spectrum generating in matlab using STFT and Filterbank approach

To analyse data in the frequency domain I often use functions like stft() in Matlab. Inspired by this video and this article I have compared the results of ...
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### How to do FFT with complex numbers - Ansi C code

I have a small issue. I'm going to do FFT2 onto a matrix $X$, and the only library I have is FFTPack. FFTPack is the oldest FFT library, but it's one of the fastest and 100% portable too. The problem ...
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### Three dimensional Wiener-Khinchin formula for incompressible isotropic random field

When I am reading Uriel Frisch's book "Turbulence", on page 55 he claimed that the Wiener-Khinchin formula for an incompressible isotropic random field, such as the velocity field of ...
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### Overall spectrum computation from Short-Time-Fourier-Transform

I am trying to computing the overall spectrum of a given signal from its Short-Time-Fourier-Transform. I am using python to do this and I wrote my function to compute the STFT: ...
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### Why do we have negative sign dB in spectrum in audacity?

I am trying to understand the spectrum of the sound of a cuckoo. It is 13-second audio clip and its download link is https://file.io/d4nqddrb1NNY Actually, I have a confusion, I have attached a snap ...
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### Separate two images using a statistical approach

So I have a fundamental question (for which I can't find a good answer anywhere). Say we have two images (A and B) and their mixed image (C) as follows: Now say that I've been given Image (A) and ...
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### Event-related EEG (epoch averaging) as a form of inter-harmonic bandstop filtering?

There is a matter that comes to my mind from time to time, now I describe it in detail. Anyway I am a first year PhD student, doing research in the field of cognitive neuroscience, but yet I only have ...
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### FMCW Radar - What's wrong with the transmitted signal model?

I am new to FMCW radar and trying to plot the transmit signal over time. As you know, the transmitted signal is modelled as: $$s(t) = cos(2\pi f_c t + \pi S^2),$$ where $S = BW/T_{chirp}$ is the slope,...
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### How to use MUltiple SIgnal Classification (MUSIC) algorithm to detect the wavenumber of a received signal at array of sensors?

I am working on analyzing data obtained from Fiber Optic - Distributed Acoustic Sensor (DAS) to estimate the properties of acoustic waves that impinge FO cable, such as velocity of acoustic waves. FO-...
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### MUltiple SIgnal Classification (MUSIC) for Frequency Estimation

I am trying to use MUSIC algorithm to detect individual frequencies of an incident signal. I read the original paper and some interesting books that explain the algorithm. I used the following ...
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### Does subtracting a phase from the frequency components of a DFT output result in rotation?

I'm currently reading a paper (Page 23 of the PDF) about the application of the Fourier transform to standardize some climatic data to easily compare them. I have the following text : 2.3 ...
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### Why does spectrum magnitude decay away from DC for positive signals?

I would like to understand why the second frequency component usually has the greater magnitude within the range [1, (N/2)], i.e why (I remove the DC component and ...
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### Decimation effect on the spectrum

If I have a sampled cosine wave signal with Fc = 80kHz and Fs = 200kHz (so the Nyquist region is between 100kHz and -100kHz) and I want to preform a decimation by the factor of 2. Will my input signal ...
1 vote
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### How to calculate energy of a signal whose frequency is varying with time (like chirp signal or any audio signal) using Fourier coefficients

If I have two audio signals, say $A_{1}$ (music) and $A_{2}$ (Speech), I want to calculate the energy of the two signals for their relative comparisons. One method I can use is by adding the square of ...
166 views

### Is it possible to predict the peak value of a time-domain signal from its frequency-domain spectrum?

As the question states, is it possible to predict the peak value of a time-domain signal given its frequency-domain spectrum? Since the time-domain signal is just the sum of the individual sinusoids ...
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### Demonstrating linear filters on daily weather data

I have daily temperature data from some place on Earth. Apparently, the sampling frequency f_s = 1/day. I would like to use these data to demonstrate (visually) the use of low-pass, high-pass, and ...
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### How to represent nonuniform resampling of signal using math functions?

I am working on optical coherence tomography algorithm. In main pipeline I should use nonuniform resampling to eliminate transformation of optical signal in IR-spectrometer (that signal disperses by ...
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### MUSIC Algorithm for 2D Power Spectrum

I am trying to use Frequency-wavenumber analysis for estimating speed of sound using two-dimensional data obtained via channel of arrays. The traditional technique is to use FFT to transform the data ...
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### What is the explanation that filter EQ changes "Ah" to "O"?

I recorded myself saying "Ah" in the tone of the note C3 which is about 130Hz, this is what it looks like: Then I ...
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### Can someone explain the phase spectrum of a sinc function?

The Fourier transform of a sinc function will result in a rect function. Suppose I have a discrete time-domain sinc function with a frequency of $\omega_0 = 0.1$ Hz and amplitude of $A = 10^{-3}$: If ...
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### FMCW Radar timing of transmission and reception

I have a question regarding the implementation of FMCW radars that seems rather basic to me, but for some reason I am a bit unclear about this. So I understand that in FMCW radar, transmitter and ...
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### Sampling frequencies calculated on paper and in MATLAB not matching

So, I've been working on a signal described by the equation $$y(t) = \cos(2\pi \ |sin(2\pi t)|).$$ On paper, I've calculated a sampling frequency of at least 2 cycles/sec, since the frequency of my ...