Questions tagged [denoising]
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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Are resolution increase and noise reduction from oversampling mutually exclusive?
Oversampling a signal means sampling it with a significantly higher sampling frequency than the Nyquist rate. As far as I know, there are three advantages:
Easier design of anti alias filter
Increase ...
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Denoising a signal using eigendecomposition
I have a complex observable series $Y(t)$ which is the result of summing two complex r.v $X(t)$ (unobservable) and a $\epsilon(t)$ (unobservable).
$$Y(t)=X(t)+\epsilon(t)$$
Assume that $X$ and $\...
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Cascading a filter with itself to form a higher-order filter?
I've been given an audio signal with some high frequency noise. The professor gave me the system function of a lowpass filter that gives me control over the cutoff frequency:
$$H(z)=\frac{1-\alpha}{2}...
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Real time background noise reduction or removal
I am trying to build a real time simple audio recognition that can recognize few keywords. Following this tensor flow tutorial i was able to train a simple neural network.
Currently the signal flow ...
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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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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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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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What Are the Differences between Super Resolution, Denoising and Deblurring?
In the fields of computer vision and image processing, what are the differences between Super Resolution, Denoising and Deblurring?
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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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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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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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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 ...
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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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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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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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Denoise Techniques When Clean Signal and Pure Noise Are 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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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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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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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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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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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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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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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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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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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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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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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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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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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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How Can I Use MATLAB to Solve a Total Variation Denoising / Deblurring 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 $ \operatorname{TV} \left( \...
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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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Additive White Gaussian Noise (AWGN) and Undecimated DWT
One of the benefits of DWT is that it is an orthonormal transform.
There are statements that the energy of noise component mainly concentrates on the high-frequency (detail) part and distributes ...
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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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How to Reduce Noise in a Video Stream?
I've been using Open Broadcaster to stream the infrared HDMI output from a 4K Sony video camera. It works pretty well, but one thing that I'm finding a little annoying for image analysis is the ...
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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 ...
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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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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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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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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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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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How Does the Non Local Means Filter Work?
As I understand,
A local mean filter is the one in which we take a pixel and calculate the mean of color-values of the pixels around them (but in a certain range of area) and the center pixel is ...
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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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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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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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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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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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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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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 ...
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Removing Noise from Dental Radiography
I'm working on a project of applying Active Shape Model to locate tooth in dental radiograph. For those familiar with the technique, I'm currently trying to sample along normal vectors for each ...
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Why do we assume the matrix of impulse responses to be a Toeplitz matrix during deconvolution
$y(n)$ = output signal
$x(n)$ = input signal
$\mathbf H$ = system response as a toeplitz matrix
$$\mathbf H = \begin{bmatrix}h(0)&&&\\h(1)&h(0)&&\\h(2)&h(1)&h(0)&\\...