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Questions tagged [signal-analysis]

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13 views

Is there a criterion that says at what point you can distinguish 2 partially overlapping Lorentzian peaks?

If you have 2 Lorentzian peaks that partially overlap and you have some frequency resolution df (your points in frequency space are separated by df) and both Lorentzian peaks have FWHM $\Gamma$ is ...
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1answer
42 views

FFT for distance-limited sum of pairwise products

I have a sequence of fixed length $N$ input arrays ($x_0$, $x_1$, ..., $x_{n-1}$), and my goal is to compute output arrays as such: $$d_{00}[l] = \sum_{i = 0}^{N - l} x_0[i]x_0[i + l]$$ $$d_{01}[l] = ...
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2answers
141 views

matched filter for doppler

To remove the Doppler shift, we can use a bank of matched filter. But, to use this method, we need an interval $[-f_{max};f_{max}]$. How can we approximate this interval?
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4answers
724 views

Why does the frequency in the DFT have to be an integer?

I don't know why the result of DFT and FFT in MATLAB like below images.. fs=128; t=0:1/fs:1-1/fs; x=cos(2*pi*3.5*t); X=fft(x); N=length(x); n=0:N-1; f=fs*n/N; plot(f,abs(X)/N); If I set the ...
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1answer
76 views

Why does it mean that the process/signal is not stationary when its variance varied with time? [closed]

Why does it mean that the process/signal is not stationary when its variance varied with time? that is, $VAR[X(t)]= \alpha \times t$,$t$ is time,and $\alpha$ is a constant,then $X(t)$ is not the WSS ...
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0answers
23 views

Correctly finding Bands(pulses) in a discrete signal

I'm trying to find a way to detect bands in a signal so that I can assign a metric to that band based off of width and amplitude. An example of the signal can be seen below, where the signal is in red,...
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0answers
53 views

spectral kurtosis binary masking (matlab)

Following this research paper, under section 4, equation 13, we can calculate the binary mask. However, I am a little bit confused on how to do this, considering I have already a complex STFT of a ...
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3answers
919 views

Power of a Discrete time signal

I was learning on power of signal and i went through different formula in internet . I get different results when i go through internet . But in other site average power is written as I dont know ...
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0answers
165 views

Why MFCC have varying length dimensions?

I have recently started to use MFCC as a feature for a project. However, I am unable to understand why MFCC have varying 2nd dimension size even when I chose the number of coefficients to be 40.
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2answers
126 views

Isolate High Variance vs Low Variance Sections of Signals

I have the following one-dimensional signals: The goal is to identify the sections with smaller variances compared to the rest (For Python, that is to get their index value in the array). In the ...
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1answer
44 views

Measure 3-D length using smart-phone's accelerometer

I'm wondering if we can measure 3-D length only by our smart-phone's accelerometer. And we all know these low cost IMUs are not accurate. You can model accelerometer's error this way: $$ a = f*a' + g ...
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2answers
48 views

Why the angle of a real signal in frequency is continuous?

This original signal is shown below (time domain): It is a real signal. According to the signal processing theory, the form part of the angle is conjugate to that of the latter part. That is, $\...
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0answers
19 views

Spectral entropy and moments and non stationary signal processing [duplicate]

What is Spectral entropy and spectral moments? I know what the normal entropy of a signal is! And also what are some good time-frequency features for the analysis of non-stationary signals?
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1answer
57 views

Detecting whether reverb is present

I have two different audio short samples of an instrument playing. If one of the samples has a reverb effect applied, how easy is it to detect which sample has reverb? Is this possible?
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0answers
80 views

How to remove echo/reflected-sound caused by stationary objects when building a ultrasound based radar

I am emitting ultrasound with a speaker and am trying to track moving objects with a microphone array by detecting doppler shifts. I have succeeded to detect movement. However, to detect the direction ...
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1answer
218 views

Carrier Recovery, Frequency and Phase offset in (CP)FSK

I wanted to ask what exactly is meant for phase recovery of signal (at least intuitively). I have a working example of an acoustic fsk modulation and demodulation software but i don't know how to ...
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0answers
118 views

Filter Bank Common Spatial Pattern (FBCSP) Algorithm

I know that for Common Spatial Pattern (CSP) algorithm i need two covariance matrices, for Filter Bank CSP algorithm i have filtered one trial of EEG signal into 9 frequency bands. My question is ...
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0answers
111 views

Graph signal processing

What's the intuition behind a ''Graph fourier transform'' ? I'm not so much interested in mathematical details or technical applications. I'm trying to grasp what a graph fourier transform actually ...
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1answer
112 views

Gaussian Equivalent of Convolving an Image 50 Times with a Box Filter

I have a image that I'm convolving 50 times with a box filter, and I like to replace this with a single gaussian filter. Because both box filter and gaussian filter are separable I can just study the ...
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1answer
266 views

How can I transform a time signal into a third octave spectrum?

I try to make a third-octave spectrum from a time signal and I have some troubles with the algorithm. I'm not an expert in signal processing so I don't know what is wrong. Here what my algorithm ...
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1answer
24 views

Investigating correlation for unequal signal lengths

I have measurements from two tablet sensors. The first sensor measures the touch pressure applied to the tablet and the second sensor is the acceleration of the tablet (in z direction). The sensor ...
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0answers
188 views

What are F0 counters in Speech signals? What is represented by F0?

I can't find any dedicated definition for Frequency F0 counters. Can anyone tell me what does F0 exactly mean, I am confused about that.
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1answer
57 views

Improvement of SNR by sampling different number of cycles using FFT of a fixed length singal

My question relates to Fourier transform of signals with different lengths in time but the same fixed length of the digitized signal with different sampling rates. Specifically, how does the number ...
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0answers
229 views

Getting the velocity in Radar FMCW

I have managed to get the frequency (the beat) frequency from an FMCW. Here is a screen shot of a wall that's detected by the Radar. I performed an FFT of complex I,Q data. My questions are 1. How ...
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0answers
57 views

autocorrelation and ISI histogram of oscillatory neuron

I'm trying to learn about different kinds of neurons and I got to a question that I'm stuck on: Given an oscillatory neuron that shoots poissonically for 50 ms and rests for 100ms:how it's ...
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0answers
39 views

Modulation Index in Case of Quadrature Modulation (IQ-modulation)

It says that in case of quadrature modulation, the modulation index can be maintained at exactly 0.5 without any settings or adjustments. I don't get it why. What is it which is making it sure that ...
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2answers
105 views

Demodulation in Rayleigh Flat Fading Channels

A core part of demodulation in Flat-Fading channels is (assuming) the channel as a(random) constant complex number multiplied with your signal. This is done in order to de-rotate the symbol for ...
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1answer
391 views

removing vertical lines in grayscale images by thickness

Suppose we have a grayscale image that contains vertical lines. Now suppose that not all vertical lines are the same, some of them have different thickness. Question is, is there a way, in MATLAB or ...
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1answer
51 views

Unexpected peaks in power density following downsampling and filtering

I first applied a 100 Hz lowpass filter to my data, which was recorded at 30000 Hz: ...
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1answer
55 views

Parabolic fiting for sub-sample precision

I am performing cross-correlation between two double[1024] arrays. I want to track the correlation's maximum with sub-sample accuracy, so I decided to implement parabolic fitting to my code. I used ...
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1answer
178 views

Wavelet transform and FFT using to extract feature power bands with EEG signals

I am using 5 channels [ fz , cz , c3 , c4 , pz] to detect drowsiness of driver My First Question is, what is the right input to get feature power band ( Theta , alpha , gamma , beta ) to wavelet ...
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0answers
206 views

How to manipulate output of Matlab's 'spectrogram' function for additional spectral analyses

all, I have an audio recording that contains several frequency-modulated elements (think animal calls like birds/bats). I have read this file into Matlab using 'audioread' and plotted the oscillogram ...
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1answer
485 views

Create a third octave spectrum from a time signal

I have to create a third-octave spectrum from a time signal on Octave GNU. I found some code on the net to help me but I don't have all the parts of the algorithm. I have a .csv file which contains ...
2
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1answer
209 views

Cross-correlation, sharp peak at 0?

First of all, I have to stress that I am not a professional of coding, no more than a professional of signal processing. I am a chemist that happen to be working on a project involving both. So in ...
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3answers
57 views

Human ear - freq log scale

I am not sure if it's DSP question or physic. But I wonder is there any math equation (method) that describe that graph? (It could be anything approximately like that). I am working on audio freq ...
3
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1answer
154 views

Phase Modulation and Intermodulation Anomaly ? (Spectrum plots inside - **Updated**)

I have a MATLAB script for modelling a two tone signal (a sum of two sinusoids) going through a non linear transfer function (such as an amplifier). The amplitude of a signal is amplified non linearly,...
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1answer
39 views

Need help deriving the energy of a signal

I am solving old exam problems in preparation of my exam in signals, and I'm having trouble with a question. For a continuous aperiodic signal with the spectrum $X(\omega)=\exp(-\omega^2)$ I am to ...
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1answer
43 views

Separate speech signals that are bandlimitted

I have 2 kind of signals (refer figures) in a folder. One is band limited to 4khz and another is band limited to 8khz, both are with sampling frequency 16khz. I need to separate them. Any idea??
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2answers
143 views

Adding phase to a signal that has multiple frequencies

An amplifier changes the phase at different amplitudes of asignal. I am using amplifier data in a MATLAB model. I have constructed a signal that is a sum of sinusoids of different frequencies with ...
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2answers
377 views

How to recover frequency and damping coefficient from superposition of damped oscillators?

I have a signal which is (more or less) the superposition of multiple damped oscillators. There are relatively few oscillators involved, 2-3 would account for most of the signal. They have periods ...
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1answer
120 views

Confusion in Peak to Average Power Ratio (PAPR)

(1) What does it mean by 'a system with low peak to average power ratio requirement'? Doesn't every system idealises it to be lower? Or there are some exceptions to it? (2) Higher PAPR can be a ...
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0answers
20 views

how to make the amplitude equal zero on the desired frequency?

I know that cut off frequency pass 0.707 from the input amplitude of the signal but I want to remove a noise let say it starts at 1700 kHz and ends at 2000 kHz how can I choose the cutoff frequency?!
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1answer
114 views

CMV: COLA constraint is not necessary

In the literature on the short-time Fourier transform (STFT) it is often stated or implied that the constant overlap-add (COLA) constraint must be satisfied in order for the STFT to be invertible. ...
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1answer
21 views

What would be the proper notation for denoting part of signal that satisfies a condition?

I have a signal $E(t)$ which start at $t=0$ and dies out overtime. What would be a proper notation to specify part of which is above a certain threshold (say for e.g. C)?. Is $E_{interested} = E(t)>...
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0answers
19 views

Can the Tonality index in psychoacoustics model be positive?

I have an issue with understanding the attached equation of Calculating the Tonality index. If you trace the equation, it appears that it is always less than 1 because the spectrum unpredictability (...
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2answers
260 views

How to edit audios so that they have the same length

I have a dataset of audio files, which differ on their lengths by a couple of milliseconds. Some are little shorter than 1s and some are little longer than 1s. They all have the same sampling rate, ...
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1answer
47 views

Power Amplifier Characterization

I am trying to characterize a power amplifier fitted to transmitter board. I applied a sinewave at the required carrier frequency and I collected the input samples and the output samples by using a ...
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1answer
120 views

Summing magnitudes of individual frequency bins

I am working on signal analyser and have problem with understanding relationship between display resolution and frequency resolution (range). My frequency range is $ 1-20000\quad [ H z ] $ so to ...
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0answers
24 views

Is it possible to find a signal that reduce the PSLR without expanding 3dB main lobe for autocorrelation?

Considering a signal $s(t) = rect(t/T_p)exp(j\theta(t))$, the autocorrelation is $ACF=IFFT(s^2(f))$. It's possible to construct the $\theta(t)$ to get a signal which has the same 3dB main lobe as the ...
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2answers
162 views

Accelerometer BMI160 changing bias

Goal: Obtain the 3-axis accelerations from the Bosch BMI160 IMU when measuring the accelerations of the bogie of a commercial train. The accelerometer used is installed in a PCB and used by an mbed ...