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Denoising is a collection of techniques to remove unwanted noise from a signal. Typically this is done by filtering, but a variety of other techniques is available. Often combinations are used in sequence to optimize the denoising.

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Recommended resources for noise reduction

I know the question What Resources Are Recommended for an Introduction to Signal Processing (DSP)? and I have already read some general DSP books, such as Rick Lyons's "Understanding DSP," and also ...
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1answer
23 views

Denoising before or after Geometric Transform?

I am working on a image which needs denoising (bilateral filter) and a geometric transformation. I am not sure in which order these filters should be applied. Personally I think it is better to use ...
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1answer
56 views

What is the name of this very simple spectral subtraction technique?

Let $S = X + N$ be the sum of two audio signals $X$ and $N$ which are both stationnary (let's think X is a constant volume 440 Hz sinusoid and N is constant volume noise). If the sum S has a -20 dB ...
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35 views

Hilbert-Huang transform - Denoising

I have a signal I want to denoise using Hilbert Huang Transform (HHT). I know, I could have used some plain methods instead, but the reason I'm using it is that 1. It's a nonstationary nonlinear ...
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1answer
36 views

The Differences between Super Resolution and Denoising and Deblurring

In the field of computer vision/image processing, what are the differences between super-resolution and de-noising/de-blurring? Thanks.
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28 views

signal denoising by continuous wavelet transform

i want to use Morlet mother wavelet for signal denoising so i should employ cwt only. Is there any proper MATLAB code for this target?
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24 views

extract trend correctly, including most recent values

I'm looking to extract the trend of a signal. i've tried two methods for now, polynomial regression, and wavelet denoising both methods don't respect the computation of the last values (meaning the ...
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1answer
40 views

Identifying whether or not a cyclostationary signal is noisy or not using the cyclic autocorrelation

I am trying to determine whether or not a given signal has been corrupted by Gaussian noise, either bandlimited (with a filter) or not. The signal in question is a BPSK or PAM signal that is upsampled ...
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1answer
37 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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1answer
77 views

Estimate smartphone accelerometer bias

I was planning to develop Android / iOS applications that enable users to measure 3D length using their smartphones. According to this question, you need to know at least the time-varying bias that ...
0
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1answer
72 views

efficient Noise cancellation & suppression algorith to use in VoIP for low latency

I am working on Noise suppression and cancellation in VoIP media engine. I am looking for noise cancellation & suppression algorithms and its implementation available with real-time low latency ...
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0answers
25 views

How to denoise ECG signals like ECG-ID database?

I'm trying to implement an identification using ECG signals. I found ecgiddb and I'm trying to reproduce the results. In each single record of this database, there are two rows of data. The first ...
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3answers
275 views

Why does signal averaging reduces noise levels by more than $\sqrt{n}$?

I have an electrophysiology signal, which is time-based. It basically measures neural activity in the form of potential differences over time. The noise in this signal is assumed to be a random ...
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3answers
203 views

Reducing noise from the same frequency band as signal

Sorry for the vague question (as I'm not even quite sure what I want to do is possible), just asking for some general direction to take my research. For a brief description, my signal resembles ...
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3answers
97 views

Denoise techniques when clean signal and pure noise is available

I have the clean version of the signal. I can obtain the environmental noise. I want to apply an effective denoising technique on a noisy signal (i.e., clean plus environmental noise). Some ...
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1answer
74 views

Measure the length of curves via a smartphone's accelerometer

Is it possible to measure the length of curves by moving a smartphone along them and processing the accelerometer's data? For example, measure the circumference of a circle of radius $8 \,\rm{cm}$. ...
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1answer
180 views

Inverse Fast Fourier with overlap

I had to work with sound(denoising algorithms), when I read about an algorithm it said that we do DTSTFT(Discrete-time short-time fourier transform) we will create an overlap between each "chunk" of ...
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2answers
97 views

Filter away sinusoidal noise properly

I have a stereo music signal corrupted by strong sinusoidal noise that varies over time. Here is the spectrogram of Left channel I plotted with Matlab. As you can see there are 3 or 4 strong ...
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2answers
90 views

recognize unwanted sounds, noises, and deleting them algorithm

I have a function that I need to use denoise algorithm on. What I thought is to divide it to smaller parts and then use Fourier Transform on each one of the parts, but I am not sure what to do next. ...
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0answers
546 views

python wavelet denoising data increase data dimension

I was recently using python package called pywavelet to denoise my data, but after the denoising process, I have noticed that the shape of data has increased by 1. my input data is a numpy array ...
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0answers
77 views

signal (EEG) segmentation and denoising, which one should done first?

Because of EEG nature, in EEG analysis often researcher use Windowing/segmentation method. As i currently work on sleep study, and in my study i need to analysis EEG data, i came to a problem. My ...
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0answers
37 views

How do I know if my EEG signal need denoising?

I recently started working on sleep study. For my research I download sleep EEG data from physionet. The EEG data has 100 Hz sampling rate and was recorded from 2 bipolar EEG site. When I start the ...
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5answers
168 views

Remove a known wav file from recorded file

I looked at many similar questions but still cannot find an answer to my problem. I'm playing an audio file N, while recording a man talking (b). The problem is that the microphone gets the played ...
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0answers
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why double desity DWT use two HPF?

The double-density DWT is an improvement upon the critically sampled DWT with important additional properties: It employs one scaling function and two distinct wavelets, which are designed to be ...
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0answers
29 views

Proof Neural Network Robustness

I am working with simple autoencoders and would like to find a bound on the reconstruction performance $\vert \vert x_{\text{in}} - x_{\text{reconstr.}} \vert \vert $ or the robustness with respect to ...
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0answers
36 views

speech transient separation techniques?

I am trying to separate a noisy speech mixture. I did several tests, for example, try to filter the speech with random broadband noise, harmonic noise, reverb, etc, but I can't seem to tackle the ...
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0answers
850 views

Noise variance in MATLAB wiener filter

I applied a white gaussian noise g=imnoise(f,'gaussian',0,0.01) to my grayscale image. Then I used a Wiener filter with ($3\times 3$) mask for denoising. In Wiener ...
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2answers
72 views

What is limit on performance of edge-preserving filters for low signal-to-noise regimes?

Let's say I have a signal, $x(t)$, defined as such, $ x(t) = \begin{cases} 0 &\text{if} \,\,\, t < -\alpha/2 \\ \frac 1\alpha t+\frac12 &\text{if} \,\,\, -\alpha/2 \leq t \leq \alpha/2 \...
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2answers
2k views

When and how does one use a Wiener filter?

I'm trying to get some insight in this topic. As far as I understand, a determined signal enters a Wiener filter and the output is an estimate of some desired signal. Then, one can substract the ...
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0answers
187 views

OpenCV denoising a 3x3 pixel pattern noise

This picture shows two photos captured by a camera from a black photographic paper. The cross is marked by laser. The left one shows a 9 pixel pattern of noise. This gets in the way of auto-focus ...
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1answer
79 views

Denoising short, non-uniformly spaced, bandlmited sequences

Consider a bandlimited signal $x(t)$ with bandwidth $BW$. Samples of this signal are observed at non-uniformly spaced sample points in the presence of noise: $y(t_i)=x(t_i) + n_i \qquad i\in\{0,1,\...
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4answers
302 views

Removing cyclic noise from signal

I'm using a sensor with output that looks like the following figure. The cyclic noise is common to ask measurements made by the sensor. Is there a way to remove the noise without negatively effecting ...
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1answer
84 views

Suggesting method for removing noise and image restoration?

Suppose that we have degraded an image with the following: $$g(n_1,n_2) = f(n_1,n_2)^{v(n_1,n_2)}\text,$$ with $v(n_1,n_2)$ being random noise which is independent from image and we have these ...
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1answer
205 views

How Can I Use MATLAB to Solve a Total Variation Denoising Problem?

The Total Variation Denoising Problem is given by: $$ \arg \min_{x} \frac{1}{2} {\left\| A x - y \right\|}_{2}^{2} + \lambda \operatorname{TV} \left( x \right) $$ Where $ $ is the Total Variation ...
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0answers
165 views

removing noise from audio

I have an audio file, in the range of 4 kHz to 120 kHz. I want to remove the lines that are not harmonic and are recognized as environment noise. the energy of the signal in this interval for each ...
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208 views

Noise reduction in extremely low SNR

I'm new to signal processing and have stumbled upon noise reduction of audio signals in a project and would like to receive some general guidelines of how noise reducers perform when the SNR goes ...
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1answer
80 views

On number of samples needed

Suppose we get $m+1$-bit signed noise samples $n_i$ with magnitude of noise as high as $m$ bits. Does averaging say $m\log m$ samples suffice to get average of $n_i$ to magnitude within few LSBs? ...
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2answers
799 views

Estimating the standard deviation of Gaussian filter from smoothed image

Firstly, let's say that in order to smooth an image, I convolve it with a Gaussian function having standard deviation $\sigma_x$ and $\sigma_y$. I am now interested in knowing if there exist methods ...
2
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1answer
132 views

Wavelet image denoising: dual-tree versus double-density

What is the main difference between the dual-tree DWT and the double density DWT image denoising techniques? How does the combination of them improve the quality of the denoised image?
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62 views

Any examples of analysis in time domain to extact information

I am sending a 20Khz signal from my phone and capturing all the signals while doing exercise above it. Here I have a signal of a person doing "hand scissors exercise" I am doing analysis on how many ...
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53 views

How to preprocess such signals?

I am interested in denoising accerelation measurements, recorded in ambient vibration tests. Such tests consist in recording the vibrations of a mechanical structure, say a table for example. So say I ...
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0answers
34 views

Smoothing for damped wave signal (fixed variance noise, but changing SNR)

My colleagues and I are arguing about how to smooth a damped wave signal. This signal is corrupted by white noise of a steady magnitude. However the signal damps out as it goes along. So, the SNR ...
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3answers
634 views

Can I square signal in the frequency domain to reduce noise?

Let's say this is the FFT of my measurements: You can see that there is a clear peak and the rest is noise. I want to reduce noise, so I square the FFT and normalize it: The peaks are now more clear,...
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2answers
174 views

Audio Denoising - Method which Extends the Naive Noise Reduction

Given an audio signal x[n] sampled at 44.1khz (let's say 1 minute of music or speech) and a noise template noise[n] (let's say 2 ...
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1answer
180 views

spectral subtraction for stationary noise

my recording was suffering from stationary background noise. I used spectral subtraction to remove it. the noise is reduced in loudness but not eliminated completely. before: http://vocaroo.com/i/...
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2answers
828 views

Gradient of Total Variation (TV) Norm in Total Variation Denoising

In this link, it says that the gradient is as follow The Gradient of the TV norm is $$ \mathrm{Grad}J(f)=\mathrm{div}\left(\frac{\nabla f}{\lVert\nabla f\rVert}\right). $$ From this other link, ...
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1answer
75 views

Can we detect multiple point target within a narrow-band transmit signal?

As I understand matched filter is optimal linear filter for maximizing the Signal to noise ratio (SNR) in presence of additive stochastic noise. Consider a radar/sonar system with narrow-band transmit ...
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117 views

Removing low frequency vibrations from measured signal

Suppose I have two sensors $s_1$ and $s_2$. $s_1$ measures the desired heart signal (with most of the frequency content below 100 Hz), and the other is a reference sensor picking mainly background ...
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2answers
184 views

sparse representation for image denoising

When I read papers on image denoising, I always encounter sparse representation. For image denoising, we try to separate image signal from noise. It is assumed that signal is correlated and noise is ...
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379 views

Noisy signal filtering MATLAB

I'm currently working on rectifying a respiratory noisy signal shown below: I've already tried to filter the noise as you can see in the image below (full image): The red one is the noisy signal ...