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

learn more… | top users | synonyms (1)

0
votes
1answer
28 views

Extra energy when altering frequency amplitudes

How can I convert a time signal (audio) into the frequency domain, multiply frequency amplitudes by a vector of scalars, and convert it back into the time domain, without messing up timing information ...
1
vote
1answer
29 views

Order analysis or order tracking

I've been trying the last week to implement the Order analyse in MATLAB in vain, I've read a lot of docs about it like this one , but I still can'T figure it out . This will be my last shot. Say I ...
1
vote
1answer
39 views

Amplitude Spectrum, Nyquist Frequency, mixed/min/max wavelets

The problem is here. Now I know the definition of mixed/max/min phase wavelets, whether the roots lie within the unit circle or not. Starting from n = 1, let $$ x_t = ( 5, 6) $$ $$ X(z) = 5 + 6z $$ ...
2
votes
2answers
54 views

PSD estimate using FFT - scaling and units

I know that similar questions have already been asked – I have read the answers, yet I am still not sure if I understand the topic properly at some points. I want to use FFT to calculate PSD ...
0
votes
0answers
32 views

Estimate SNR of Spread Waveform?

Suppose you have a sinewave at an aribitrary frequency, $f_0$, and you spread it (chip it) with a spreading code of length, $N$, with an arbitrary chip rate: What is the loss in SNR as a function of ...
0
votes
1answer
59 views

use prony method for damped exponentials

let us consider represented of damping exponential model by prony method,there is source code ...
0
votes
0answers
35 views

Why the radar (moving) target return is not centered at zero frequency

In Radar signal processing, one has to separate clutter(unwanted signals) from moving target signals. The picture given below is an example of Radar Signal Power Spectum(taken from the book Radar ...
-1
votes
0answers
18 views

Signal envelope's frequency content and denoising by SVD

How is the frequency content of an envelope of a signal related to the the signal's frequency content ? I am a bit confused here. Is there a theoretical expression relating the two ? I am reading this ...
0
votes
1answer
41 views

use chirp z transform for spectral resolution

let us suppose that we some signal $x(t)$,which consist of sinusoidal components and white noise,i would like to know how to use chirp z transform for improving spectral resolution?i found this ...
0
votes
1answer
25 views

Convert normalized frequency to real frequency in AR model

Let us suppose that we have modeled signal using AR model, and suppose we have following model: I used spectral estimation function from MATLAB pyulear Now ...
0
votes
0answers
12 views

PSD estimation from multivariate data [migrated]

Assume a multivariate dataset $\mathbf{x} = (x_1, ..., x_n)$ where $x_{i}$ are for example different sensors. Now, there are several techniques (e.g. Welch's method) to calculate the power spectrum of ...
1
vote
0answers
79 views

Yet Another Peak Detection Request

I looked over the other entries regarding peak detection and none seem to answer my question. I'm working with Fourier spectra of digitized audio that can't be measured again. There are no ...
0
votes
2answers
33 views

Using Least Squares for curve fitting in Matlab

I have a problem right now to solve. I have a Gaussian peak, which I need to divide into three components (three Gaussian distribution). For those three component Gaussian distribution, I already know ...
0
votes
3answers
64 views

A question about spectral leakage

I have read about spectral leakages in other posts here. From what i understand, it occurs because you dont have an integer number of time periods in your sampled data. By default a rectangular window ...
0
votes
1answer
60 views

Spectral Envelope from MFCC

I'm obtaining MFCC by using the function wave2mfcc from the Speech and Audio Processing library (SAP) from here http://mirlab.org/jang/matlab/toolbox/ The steps follows the procedure: Take the ...
1
vote
1answer
305 views

Upsample data using FFTs. How is this exactly done?

I am basing my question on this post here, because I would like additional details on it, as I have not had any success in re-creating it. I would like to simply learn, in no uncertain terms, how to ...
0
votes
2answers
125 views

Measure the SNR of a signal in the frequency domain?

How do you measure the SNR of a sinewave in the frequency domain? (Assuming no filtering.) Suppose: $$x(n) = s(n) + n(n)$$ Create the signal (nCycles of a sinewave) in MATLAB...: ...
1
vote
1answer
98 views

Fourier Transform for frequency analysis

I applied Fourier transform on a sound (PCM generated digitally with sin function) and frequency detection is accurate. However, if I play the sound and record it, and then apply a Fourier transform ...
1
vote
1answer
63 views

Which kernel produces sharper image

kernel A = [ 0 -1 0 -1 4 -1 0 -1 0 ] and B = [-1 0 -1 0 4 0 -1 0 -1 ] i have found the frequency spectrums with ...
2
votes
1answer
32 views

Is there an analogue of coherence between data sets related by a non-linear transformation?

Calculating the coherence (sometimes called magnitude squared coherence) between two signals indicates the presence or lack thereof of a linear transformation between the two signals. Is there an ...
0
votes
0answers
20 views

Finding Signal Energy of a continuous signal in the time domain

I have a quick concern regarding an assignment that I'm working on. Currently, to find the signal energy of a continuous signal, we're converting the signal to the frequency domain through a fourier ...
0
votes
0answers
35 views

bearing frequency detection

I am working on bearing faults detection. I am doing the following steps: signal->mean zero->high pass->hilbert->y->fft->cepstrum of y. my code is: ...
0
votes
0answers
44 views

cepstrum analysis to get fundamental freuquency

I am trying to find the fundamental frequency of a bearing fault.This is my code c2=cceps(abs(Signal_fft_hilbert(2:250))); plot(freq_s(2:250),c2) And this is ...
0
votes
2answers
151 views

Convolution in the frequency domain

We often hear that "convolution in time is the same as multiplication in frequency", and vice versa, that "convolution in frequency is the same as multiplication in time". So in a typical windowing ...
1
vote
2answers
81 views

Spectrum analysis : how to represent FFT results

I'm trying to program a spectrum analyser in C++ but I'm faced with a conceptual problem : how to map the results of the FFT to an image ? Let me detail : I'm doing all this in a dynamic way. I ...
0
votes
1answer
57 views

adjusting swept signal equation

When I do a spectrogram in matlab / octave I can create a swept signal that looks like the RED plot line below. But how can I create a swept signal like the BLUE line in the 1st plot using the ...
0
votes
0answers
34 views

Segmenting Audio File - Considering time

I can't seem to figure out where I'm going wrong here.. I have the following spectrogram: I'm trying to segment the spectrogram into 3 parts, essentially, I will just have 3 signals (the ones with ...
0
votes
1answer
62 views
0
votes
0answers
39 views

Calculating hertz / kHz

Over the past few weeks, I have been working on a problem of segmenting an audio file containing some bat samples. I have now successfully come up with a moderate algorithm to do this. I am trying ...
0
votes
3answers
91 views

Mixed time/frequency domain data

I'm afraid this might be a bit of an elementary question, but I'm afraid I'm a little new to this. I've got a system that measures a frequency spectrum to find resonant frequencies. It does this by ...
2
votes
3answers
74 views

Detection of wobbling sound with rising notes

In an audio file I would like to find calls of a specific bird specie, one that makes wobbling sound with rising notes. Can you recommend what would be the best audio feature to calculate in time or ...
1
vote
1answer
53 views

How does integration of a signal change the spectrum?

It's a very basic question, but I havn't found the question on google or dsp.stackexchange.com: How does integraion of a signal change the spectrum?
2
votes
1answer
67 views

Effect of sampling interval length and Gaussian noise on the frequency-spectrum

Suppose you have a signal $s(t)$, corrupted by Gaussian noise of $\eta(t)$ with zero mean and standard deviation $\sigma$. So that the measured signal is $f(t)=s(t)+\eta(t)$. I now want to calculate ...
-1
votes
1answer
46 views

Which FIR filter should I choose?

If I have the following spectrogram: And only wanted to have the signals that are in a particular frequency range (2627 - 3939htz).. Can I run a FIR filter to only allow these signals through, and ...
-1
votes
1answer
80 views

Classifier for detecting sound over noise [duplicate]

Suppose I have the following signal (Spectrogram): I have three types of elements that I want to identify within this signal: 1) Noise 2) Call-1 3) Call-2 I ...
0
votes
1answer
46 views

Interpret numpy.fft.fft2 output

My goal is to obtain a plot with the spatial frequencies of an image - kind of like doing a fourier transformation on it. I don't care about the position on the image of features with the frequency f ...
1
vote
1answer
127 views

Normalized frequency in matlab

I have a progam in matlab that generates a linear and quadratic chirp, and now I want to study the frequency components in wvtool. However, I am not able to decode the frquency domain scale "the ...
0
votes
1answer
59 views

Normalizing a spectrogram or a pitch class profile

I am developing a chord recognition program using neural networks.I need to normalize the spectrogram or my pitch class profile to provide inputs for the neural network. The pitch class profile ...
2
votes
2answers
79 views

minimum SNR requirements for maximum likelihood frequency estimation

In certain applications, you have enough SNR available to, for example, perform an FFT and identify peak location and hence the signal frequency. If my understanding is correct, parameter estimation ...
1
vote
0answers
38 views

What are variance and bias in spectral estimation (specifically periodogram spectral estimation)?

So far, I have read that all the non-parametric estimation techniques decrease the frequency resolution in order to decrease the variance in the spectral estimate What is the general "overview" ...
3
votes
0answers
62 views

What assumptions should be used to invert spectrum into time domain data?

This question comes from a realistic problem that how to obtain a time domain wind pressure from known wind spectrum. Or similarly, gets rail surface curve from spatial rail spectrum. Obviously, ...
1
vote
2answers
99 views

dBFS scaling and spectrum

I am trying to replicate the spetrum as given in Audacity and other commercial software... I am getting crazy with the correct scaling needed in order to have dBFS (with reference to a full scale sine ...
0
votes
2answers
59 views

Estimating the amplitude of a particular frequency

I am relatively new to DSP and have been reading a lot on the internet. I have a couple of questions. I have a signal in the form of a function $$ f(x) = A_0 + A_1 \cos(\omega_1 x) + A_2 ...
3
votes
2answers
94 views

Spectral images - How do they appear during ADC?

Why is it that spectral images appear? I know they appear for $F_s$, but why those replicas appear, I don't know. E.g., sampling $x(t) = sin(1000 * 2\pi t)$ with a sample frequency of 230 Hz. I know ...
1
vote
2answers
68 views

Do DSP principles apply in the same way to both Audio and EM spectrums?

All of my DSP experience is very much centred in the EM spectrum and I've only ever processed EM-type signals in the past. I'm now doing quite a bit of work in ultrasound and the audio spectrum, ...
1
vote
2answers
103 views

Analyse audio/music frequencies without STFT, at 1/f temporal resolution, using probe phasors at logarithmically-spaced frequencies, O(N log N)?

First, some background: The STFT is the best general-purpose tool I know of for analysing a (musical or other) signal into its component frequencies. For many purposes the STFT works fine, but there ...
3
votes
2answers
343 views

Plotting magnitude and phase for frequency spectrum

I would like to find the frequency spectrum by drawing magnitude and phase for the following signal: S=sin(2*pi*100*t)+cos(pi*500*t); X=sinc(2*pi*t); Is there ...
0
votes
2answers
71 views

efficient spectrum/fft analysis of sparse signals (found in radar applications)

consider the classic scenario of identifying a radar frequency. You typically have a very short pulse of very high RF frequency. For example, a 50ns pulse repeating itself every 1MHz or so (PRF 1MHz ...
1
vote
0answers
111 views

Spectral Correlation Function estimation using FAM method — implementation help

I am trying to estimate the Spectral Correlation Function by the FFT Accumulation Method (FAM) in Matlab. The way I understand the FAM method is as this link (see page 6 & 7 for FAM tutorial). ...
0
votes
1answer
61 views

How do I compute the DC component given the other part of the Fourier spectrum?

I often see examples in textbooks where someone constructs a 2D Fourier spectrum of an image by fixing two (symmetric) pixels to a given value, and computes the inverse DFT to get a nice waveform ...