# Questions tagged [signal-analysis]

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### How to make sense of audio file's $\textrm{dBFS}$?

I'm trying to build a song visualizer using the FFT method. When I analyze the audio, I get the $\textrm{dBFS}$ value for each frequency range. From my understanding, $\textrm{dBFS}$ is in the range ...
119 views

### How to apply baseline methods to MNE preprocessed raw EEG signals?

I am new at EEG preprocessing and classification. I have followed Clemens Brunner's blog https://cbrnr.github.io/2018/01/29/removing-eog-ica/ as a tutorial for MNE. This is how I have preprocessed ...
27 views

### Measuring Phase Difference at DC bin aliased frequency using FFT

I have a code in which two complex signals (I/Q) are created having same frequency but with phase difference. FFT of both signals is taken and atan2 is used to compute phase after which the difference ...
50 views

### Confused in Smoothing a signal in the Frequency domain

First of all i am new in DSP, so i have no solid education in the field. I have convert my time domain acceleration-seismic data to frequency using DFT and i am trying to smooth the DFT data, in ...
71 views

### What is issue in square wave reconstruction?

As shown in attached photo: What is the reason that the approximate square wave $$x_N (t)$$ at right side is not like the original $$x(t)$$ at left side .? Is the only reason is that number of ...
50 views

### Confusion regarding sinusoidal synthesis formula,

I am reading signal processing first by McClellan As shown in attached snapshot, we have formula of sinusoidal synthesis I am confused ,why in expression of x(t), there is a '2' in first line ...
32 views

### Wind turbine vibration analysis approach

This is going to be a bit of a long post. My questions are: Do the 5 signal processing steps look "correct"? Next steps could be to perform order analysis, and extract features from time, frequency, ...
54 views

### Confusion regarding calculation of fundamental period?

I am reading signal processing first and in chapter 3 ex3.8 i came across an example of fundamental period as shown in attached photo It apparently shows that signal $$x(t)=\cos^2(4\pi t)$$ has ...
26 views

### How to approach Feature Extraction and Feature Selection part in machone learning in python?

I am a bit new to machine learning and I have the following questions: Question 1: When dealing with feature extraction with signals from sensors, what is the typical approach to extract features ...
44 views

### Is it true that each and every signal has multiple frequency components?

Usually when we observe spectrum of a signal,we see multiple frequency components, each having different contribution to amplitude But is it true that each and every signal has multiple frequency ...
52 views

### Feature extraction for exponentially damped signals

I am looking into exponentially damped signals where it is a stationary signal (after implementing the Adfuller statistical test) and I would like to look into how can I extract meaningful features ...
116 views

### Detect Gradual Increase Before a Decrease in Noisy Data

I have data that'ss not too noisy and I am trying to detect a pattern where it gradually increases then decreases in a short period of time (20 ticks? it should be roughly similar per session but can ...
71 views

### Channel estimation and interpolation by vector in OFDM

I have V-OFDM system (Vector OFDM) where every symbol is organized as in below figure: The black cirles are pilots and white circles are data. First, iFFT operation it taken per column, and then ...
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### Type of filter, given difference equation?

Given a difference equation, how do we tell if it is an IIR filter or FIR filter? For example, y(n) = x(n-3)+y(n-1) . Is it FIR or IIR? Can you please give me a way to figure this out? Thanks! :)
474 views

### Convolution of an Image with a Kernel That Is a Product of Two Functions

Suppose that $G(i,j)$ is a Gaussian decay function on the distance between points $i$ and $j$ of an image. In addition, $D(i,j)$ is the difference between the VALUES of the image at those points. Now,...
1k views

### Ambiguous results of phase correlation in pattern recognition

We are using phase correlation to find pattern on image and what we get is 15% of results is spurious. Ours pattern has 32x32 pixels and image for research has 32x512 pixels. So we put Pattern to ...
9k views

### What does fir1 in matlab does?

May i know what does this function do in matlab? num = fir1(80, [5Hz, 50Hz]); I know that 5 Hz is the low cut-off freq and 50 Hz is the high cut-off freq. I'm ...
13 views

### Spectral kurtosis on non-stationary signal

I posted a question some weeks ago I still have not found an answer to. I updated the old question and am hoping someone could help. Link: Varying speed of shaft Spectral Kurtosis
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### Varying speed of shaft Spectral Kurtosis

I want to perform Spectral Kurtosis (Kurtogram) on 10-second vibration signal of 25.6 kHz sample rate, where the shaft is varying in speed. Will a preprocessing step of resampling the signal be ...
43 views

### How to find if the signals are in sync or out of sync with each other?

Considering these are two signals over time, black and red.Following are some of the properties Every Second a new data point is added over time . There is no control on the generation of the ...
1k views

### Corner detection using Chris Harris & Mike Stephens [duplicate]

I am not able to understand the formula, What is $W$ (window) and intensity in the formula mean, I found this formula in opencv doc http://docs.opencv.org/trunk/doc/py_tutorials/py_feature2d/...
198 views

### How to detect the maximum resolvable spatial frequency of camera?

I am trying to calculate the minimum line pixel width that can be distinguished from noise as shown in the camera test chart in Figure 1 where the thinner lines on the left are getting more and more ...
2k views

### How do I compare chords played on a guitar with a known sample?

I want to create a project that will recognized the chords that i played in guitar. I recorded a raw sound to be compare to the one that the user will input. Example I have a recorded sound chordA ...
552 views

### Detecting a frequency pattern in the frequency domain

I am looking to detect a combination of frequencies in the frequency domain. For example, here is my spectrum: And I'm trying to detect the pilot tone. I have the FFT of the pilot tone: which zoomed ...
8k views

### How to use low pass filter in Matlab for discrete data? [closed]

As see in the picture, there are high frequency noise in the signal. How to design a low-pass filter to eliminate the noise? How to apply this filter in Matlab?
24k views

### noise of zero mean and variance?

It might be a very silly question, however I'm facing problem with it. Now, the Gaussian noise is a signal with zero mean and variance. I understand what the mean and the variance mean however, I'm ...
2k views

### How can I find the actual frequency given a normalized frequency?

Suppose that we have some sample: ...
581 views

### Power of summation of two signals

Let $|A|$ denote the power of the analog signal $A$. Is that true to assume $|A+B|=|A|+|B|$, for two arbitrary signals $|A|$ and $|B|$? That is the power of the summation of two signals is -at least ...
930 views

### Ways to compute the n-the derivative of a discrete signal

This is a pretty general question about how to compute derivatives of a digital signal $x[n]$. I would like to know what are the different approaches (from naive to complex) and how are they compared ...
251 views

### Can I construct a linear system so that it results in a moving average?

I've just learned about linear systems and impulse response functions. I know that in a linear system consisting of $h_1[k]$ and $h_2[k]$, the impulse response of the system is $h_1[k] \ast h_2[k]$. ...
241 views

### Getting different results when running my program at different times [closed]

I am working on Speckle Noise reduction in Ultrasound Images using MATLAB R2013. I have designed 10 basic filters and trying out hybrid combination using these filters. When I run my program I get ...
4k views

### How to separate a low amplitude signal of same frequency but different phase

I have a signal consisting of two sine waves of same frequency but have different phase (and also a lot of HF noise). Their amplitudes differ by about $120\textrm{ dB}$. How to I go about separating ...
1k 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 ...
72 views

### Rectify signal basic question

When rectifying a signal by squaring it, is it necessary to upsample by a factor of 2? Why is this?
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### Is it possible to detect or localize movement of objects using LPWA (or LPWAN) such as LoRa, DASH7, NB-FI?

Assume that there is a moving human in the room without any device (or receiver). Is it possible to detect or localize movement of objects using LPWA (or LPWAN) such as LoRa, DASH7, NB-FI by analyzing ...
50 views

### How to make signal smooth using filter?

I have measured the output of a mechanical system and obtained the signal shown at the attached image. I want to make it smoother by removing the chattering (I think it is called chattering). In order ...
32 views

### Time domain to angular domain approach

I have a rotating shaft where I need to move from the time domain to the angular domain to look for vibration faults. I have the data from a tachometer. From another post I found these steps: The ...
43 views

### Upsampling question- Aliasing/imaging problem

I'm trying to study vibrations in a non-stationary shaft by upsampling the original signal. The original sample rate is at 25.6kHz, and it is being upsampled to 36kHz. In the FFT of the upsampled ...
53 views

### What is the effect of padding zeros to FFT on time domain ? (opposite of what is usually done)

As above. I know that zero padding in time increasaes frequency resolution but I'm having a hard time to understand the opposite. How would you interpret that?
202 views

### Significance of sequency ordering in Walsh-Hadamard matrices

So I've been doing some reading into Hadamard and related matrices (Slant, Walsh, , and have observed that there are three typical "orderings" of the rows based on various criterion. E.g. "Natural", "...
294 views

### RADAR Video Signal and Matched Filtering

In order to make my question more clear and give more details I'm trying to understand the processing signal procedure in radars,i understood till this moment that a transmitter generates a signal ...
309 views

### CFAR Detectors and Interference

Constant False Alarm Rate (CFAR) is an automatic thresholding technique. It's situated after the FFT processing in other to detect target peak. This probability of detection depends on clutter and ...
56 views

### Similarity or Relation between Walsh Hadamard Transform and Slant Transform

Is there any relation between Walsh Hadamard Transform and Slant Transform? Or is there any common property or similarity?
79 views

### About the variance of the coefficient of narrowband noise when using signal-space representation

Assume that n(t) is a white Gaussian noise process with zero-mean and power spectrum density $N_0/2$. By using the signal-space representation, it can be expressed as: n(t) =\sum_{j=1}^N n_j \...
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### Why Cross-correlation work better than Generalized Cross-correlation GCC-PHAT in MATLAB?

Fs = 192000; t = 0:1/Fs:(0.01-(1/Fs)); F1 = 10000; x = 1*sin(2*pi*t*F1); nSamplesGausswin = length(t); w = (gausswin(nSamplesGausswin))'; s = w .* x; this is ...
14 views

### Transforming acceleration to a world reference

I have a acceleration data relative to the sensor's coordinate and the sensor's rotation relative to the world coordinate.How can I transform the acceleration from the sensor's coordinate to the world'...
117 views

### Removing Noise from time across signal data

I am new to the field of signal processing. I have sensor data (Impedance across time), that output is like this. On the right side, I have a noisy signal portion in my data, marked by the red block....