Questions tagged [noise]
In signal processing noise can be considered random unwanted data without meaning.
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Why is TV static noise always black and white?
Most modern day Cathode Ray Tube (CRT) televisions manufactured after the 1960s (after the introduction of NTSC and PAL standards) supported the circuit-based decoding of colored signals. It is well ...
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Variance of White Gaussian Noise
It could seem an easy question and without any doubts it is but I'm trying to calculate the variance of white Gaussian noise without any result.
The power spectral density (PSD) of additive white ...
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Bag of Tricks for Denoising Signals While Maintaining Sharp Transitions
I know this is signal dependent, but when facing a new noisy signal what is your bag of tricks for trying to denoise a signal while maintaining sharp transitions (e.g. so any sort of simple averaging, ...
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Pink ($1/f$) pseudo-random noise generation
What are some algorithms for generating a good pseudo-random approximation to $1/f$ (pink) noise, yet suitable for implementation with low computational cost on an integer DSP?
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How to distinguish voice from snoring?
Background: I'm working on an iPhone application (alluded to in several other posts) that "listens to" snoring/breathing while one is asleep and determines if there are signs of sleep apnea (as a pre-...
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How to Generate Band Limited Gaussian White Noise in MATLAB?
In some papers, I read that the additive noise is band limited Gaussian white.
How can I simulate this type of noise use MATLAB?
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human speech noise filter
Does anyone know of a filter to attenuate non-speech? I am writing speech recognition software and would like to filter out everything but human speech. This would include background noise, noise ...
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What is the phase and magnitude response of white noise?
I would like to create white noise in the frequency domain, and then transform it to the time domain using python. To understand the problem, I simply generated white noise in the time domain, and ...
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How do I add AWGN to an I and Q representation of a signal?
I have a wireless communication system that I am simulating in Matlab. I am performing some watermarking through slightly adjusting the phase of the transmitted signal. My simulation takes the ...
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Determining the "whiteness" of noise
How does one quantify how "white" some noise is? Are there any statistical measures, or any other measures (FFTs for example) that can quantify how close to white noise a particular sample is?
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How to Remove Gaussian Noise from an Image without Destroying the Edges?
What is the best filter for removing Gaussian noise without destroying the edges? I am using the standard Lena images with additive Gaussian noise and I want to denoise before applying anisotropic ...
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What mathematical tools exist for understanding modulated noise?
Suppose we have a signal $n$ that consists of Gaussian white noise. If we modulate this signal by multiplying it by $\sin 2\omega t$, the resulting signal still has a white power spectrum, but ...
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Wiener Filter for Image Noise Reduction (Image Denoising)
I'm trying to get my head round the operation of the Wiener filter for the purpose of image noise reduction. In my case I'll have used another noise reduction filter first and will then use the result ...
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How do I determine whether I have pattern-free noise?
For microscopy, we're frequently testing cameras. Since my applications involve very low signal-to-noise ratio, it becomes important that the noise is free of correlations and patterns, because local ...
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Relationship between entropy and SNR
In general any form of enropy is defined as uncertainty or randomness. In a noisy environment, with increase in noise, I believe that entropy increases since we are more uncertain about the ...
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Kalman filter - understanding the noise covariance matrix
What is the significance of the noise covariance matrices in the Kalman Filter framework?
I am referring to:
process noise covariance matrix Q, and
measurement noise covariance matrix R
at any ...
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What are the various definitions for $\rm SNR$, and their associated methods for measuring it?
The definition of $\rm SNR$ seems to be somewhat of a tower of babel in industry. What definitions of $\rm SNR$ are there (feel free to site application), and how exactly can it be measured for that ...
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Estimate Sine Frequency under White Noise — simple and effective method
Given a sinusoidal signal in white noise, how can one efficiently determine its frequency?
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What are the statistics of the discrete Fourier transform of white Gaussian noise?
Consider a white Gaussian noise signal $ x \left( t \right) $.
If we sample this signal and compute the discrete Fourier transform, what are the statistics of the resulting Fourier amplitudes?
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Detecting drum bpm in a noisy .wav file
I am looking for algorithm(s) to solve the following problem:
Given a noisy .wav sound capture (some wind + friction noise on the microphone), how to detect the BPM of a soft drum beat?
I have ...
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ADC performance simulation: How to calculate SINAD from FFT?
While working on this problem, I started to have doubts that my initial definition of
$$SINAD = 10 \log_{10} \left( \frac{p_f} {\sum_i{(p_i)} - p_0 - p_f} \right)dB$$
is correct. In this equation, $...
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Why is random noise assumed to be normally distributed? [duplicate]
From residual in the linear regression to noise in signal processing are assumed to be normally distributed? By considering them as normally distributed we are kind of telling the pattern in the noise ...
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Why do I see ringing in the output of a digital filter with a narrow transition band?
I am doing some 'extreme' eq for spectral mangling type effects with audio. Im using brick wall filters, and very narrow band pass and reject filters (vst plugins), and I'd like to know if there's ...
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How does the quantization error generate noise?
I'm learning about sampling and DSP on my own. I have a hard time to understand how the quantization error results in noise. I think I miss a fundamental understanding but can't tell what it is. So ...
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Parametrically degrade the speech to remove emotional content
I am happy to accept suggestions either in R or Matlab, but the code I present below is R-only.
The audio file attached below is a short piece of conversation between two people. My goal is to distort ...
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Peak Signal to Noise Ratio (PSNR) in Python for an Image
How do I calculate the maximum signal to noise ratio (PSNR) in Python? Is there any library that can calculate PSNR for Image?
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What is the difference between 'de-noising' and what we commonly know as filtering methods to remove noise?
Pretty simple question - I am trying to figure out what exactly is different between 'de-noising' a signal, and simply filtering it (as we commonly know) to remove noise. Is this a case of lexical ...
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Effect of windowing on noise
I understand that truncating a signal in time 'smears' the frequency response depending on the window chosen. In general, the shorter the signal duration, the more 'flattened' the frequency response, ...
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Where can we find noises like Gaussian, Rayleigh, Gamma, exponential noises in real world images?
I know that while taking pictures from a camera, noise may appear in the image.
It is often described as Gaussian, but what about the other noises, when do they occur in real world?
Please help!
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Approximating the frequency response of a median filter
A median filter is a non-linear and lossy process, so it doesn't have a closed form frequency response as would a FIR filter (say a box filter of the same length) in an LTI system.
But how closely ...
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Smoothing signal / detecting bumps in a data stream
(EDIT: This question follows from Extracting Binary Magnetic-Strip Card Data from raw WAV)
Here is my signal (top line) and a basic IIR filter applied (bottom line)
(EDIT: my task is to break the ...
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How can you tell whether there's a signal (when your signal looks a lot like noise)?
This is my snoring detector again.
I've gotten pretty good at detecting a signal when there's anything there -- can track from a wall-peeling snore down to breathing you can't even hear in the ...
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Recover curves from noisy collection of points
Background: I'm trying to make a system that tracks a number of bubbles in a video
I'm implementing the bubble detection in the single image case using the Circular Hough Transform. Due to occlusion, ...
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Removing noise from F2F signal
(This question relates to Extracting Binary Magnetic-Strip Card Data from raw WAV)
I am extracting the binary sequence from the magnetic strip on a credit card.
As you can see, the signal is ...
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Zero Crossing of a Noisy Sine Wave
I'm trying to find the zero crossings of a sine wave to transform the sine wave into a square wave. The only problem is that the sine wave is noisy, so I'm getting lots of jitter and false zero ...
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Estimate Taylor series coefficients from samples of a function
Say I have measurements of a function $y = y(x)$, sampled at $x_i$ with some noise, that could be approximated by a Taylor series expansion. Is there an accepted way of estimating the coefficients for ...
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What is the connection between analog signal to noise ratio and signal to noise ratio in the IQ plane in a quadrature demodulation system?
We would like to compute the quantitative relation between analog noise near the LO frequency and the statistics of points found in the IQ plane after IQ demodulation.
In order to completely ...
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peak limiting/audio compression formula needed
I'm looking for a formula to effectively compress an audio waveform to limit peaks. This isn't an "automatic volume control" application where one would control amplifier gain to maintain a volume ...
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Is the Kalman Filter a Best Linear Unbiased Estimator (BLUE) for Heteroscedastic Noise?
According to the Gauss-Markov Theorem, a ordinary least squares estimator is BLUE if the noise entering a system is uncorrelated with zero mean and is homoscedastic (has a constant finite variance). I ...
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Deconvolution with noisy measurement of impulse response function
I observe a noisy complex-valued signal that has passed through some linear time-invariant filter:
$$y(t) = (h * x)(t) + n(t)$$
where $h(t)$ is a causal and finite impulse response, and $n(t)$ is ...
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How does noise reduction for speech recognition differ from noise reduction that is supposed to make speech more "intelligible" for humans?
this is a question that has interested me for some time now, mainly because I'm working on noise reduction for an existing speech recognition system myself.
Most papers on noise reduction techniques ...
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What is obtained from the cross correlation plot?
Let’s assume that we have two audio signals, x(t) and y(t) affected by the noise as shown below.
And we would like to cross-correlate these two signals and the cross-correlation plot is shown as ...
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Solving Convex Optimization Problem Used for High Quality Denoising
The highest voted answer to this question suggests that to denoise a signal while preserving sharp transitions one should
minimize the objective function:
$$ |x-y|^2 + b|f(y)| $$
where $...
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Why is Gaussian noise called so?
Can you please explain: why is a specific type of noise called "Gaussian noise"? Why is it relevant to call it Gaussian? Please, explain in layman's terms.
user18425
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Gaussian White Noise - Relation Between Distribution and Correlation
Im a beginner in signal processing so my question may be obvious.
A white noise has the property to have its autocorrelation function that is equal to
$$\mathbb{E}[f(t+\tau)f(t)]=\sigma^2 \delta(\...
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limit to possible noise shaping?
I want to do noise shaping in a 100kHz, 16 bit application, so as to shift all quantization noise to the 25khz-50kHz band, with minimal noise in the DC-25kHz band.
I set up mathematica to create a 31-...
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Improving Digitization by Adding White Noise Before Oversampling
I was reading a physics book and it said that when digitizing a signal white noise was added to improve the process. I don't understand how this works. Therefore my question is:
When digitizing an ...
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How to estimate the signal-to-noise ratio of a waveform?
I have a signal: $f_i(t_i=i\Delta t)$, where $i = 0\ldots n-1$.
The signal seems to vary quickly around a slower varying "trend". I am assuming that the quickly varying part is noise and the slowly ...
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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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What is the type of noise in this image?
what reason could make the noise/effect in this image?
Below is the original
Thanks!
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