Questions tagged [noise]

In signal processing noise can be considered random unwanted data without meaning.

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19
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3answers
58k views

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 ...
19
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3answers
5k views

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?
3
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2answers
2k views

Noise detection

I was wondering if someone could suggest a method to differenciate between two signals, on algorithmic scale for example a criterium to calculate, that shows how noisy a signal is, i have found a post ...
16
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5answers
22k views

How to Generate Band Limited Gaussian White Noise?

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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4answers
5k views

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-...
16
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1answer
19k views

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 ...
9
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2answers
2k views

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.
14
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3answers
6k views

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?
3
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2answers
3k views

How to remove or filter the drift problem in measured Strain signal?

I have the strain signal of a lateral beam of a car measured at sampling rate 1,200Hz from data acquiring system. Even after using temperature compensation in strain gage, we are getting drift. So I ...
9
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1answer
1k views

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 ...
6
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4answers
2k views

How to recognize patterns in a noisy audio frequency spectrum?

I have an audio spectrum (FFT) that looks like this: ...
12
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2answers
1k views

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 ...
7
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2answers
4k views

Which domain used for denoising additive and multiplicative noises

I want to know what is the difference between additive noise, multiplicative noise.. In what domain these noises are handled to remove? I am interested particularly in image dataset Does different ...
2
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1answer
1k views

what's gaussian noise look like?

I am using Matlab function imnoise to add gaussian noise to one image. However, it seems that adjacent samples of the noise is correlated. I am using matlab code below to add noise. ...
21
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4answers
3k views

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, ...
9
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4answers
8k views

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 ...
1
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1answer
720 views

What is best practice to remove static noise?

What is best practice/algorithms to remove static noise from speech ? static noise aka Stationary Signal/static noise due to 1.humming sound due to of telephonic line/channel, 2.moving Vehicle,or ...
12
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1answer
3k views

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 ...
10
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2answers
651 views

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 ...
5
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1answer
2k views

How to choose FFT depth for ADC performance analysis (SINAD, ENOB)

I am trying to simulate a model of an ADC and determine its performance. One of the interesting properties is the ENOB (Effective Number Of Bits), which can be calculated from SINAD (SIgnal-to-Noise ...
8
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4answers
594 views

How to determine the “variability” in a frequency range?

This is a continuation of a previous question. I'm trying to analyze breathing and snoring sounds, and while I can fairly well detect snoring now, breathing is a bigger challenge. I've learned that ...
5
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5answers
8k views

why Gaussian noise is usually used?

Gaussian noise with different SNR levels are usually used in research works to simulate a realistic environment. How can researchers guarantee that Gaussian noise can simulate the reality of a System?
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5answers
6k views

Derivative of noisy signal

My input signal is phase vector. I want to differentiate it to get frequency vector. My input signal is somewhat noisy. Here is the input signal. This is the derivative of the input signal as ...
3
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3answers
515 views

Comb filter - attenuation

I have a signal and from 'standard information' I know the predominant frequency is at $1\textrm{ Hz}$ and then there should be three harmonics at lower amplitudes. My signal however has a lower ...
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2answers
820 views

Fourier transform of a Fourier transform

I generate a Gaussian noise and then I filter it with a passband FIR Kaiser window filter. When I perform the Fourier transform of the output of the filter and plot its magnitude spectrum, it is ...
1
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1answer
3k views

How to Simulate AWGN (Additive White Gaussian Noise) in Communication Systems for Specific Bandwidth

I am trying to generate a AWGN waveform to add it to the signal of my simulated communication system. The operating bandwidth of the communication system is about ...
8
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2answers
3k views

What is the math behind median filter's noise reduction property?

I am interested in understanding the mathematical reason for why does applying a median filter on an image (or signal) result in reduction of noise.
1
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2answers
2k views

white noise in images

For digital images, noise is assumed to be additive gaussian white noise. I remember noise in images is considered as high frequency. However, from the link https://en.wikipedia.org/wiki/White_noise, ...
0
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1answer
51 views

Recommendations for SINAD equipment

I am interested in buying a device that measures the SINAD of the audio signal(FM signal) that I receive from PC. Here is the setup: Signal generator (generating 1kHz FM signal ) $\rightarrow$ ...
0
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2answers
2k views

Compute the time derivative of a noisy digital signal?

The issue is that my signal is very noisy. I need extract its time derivative as accurate as possible. P.S. I do not have any prior knowledge on the signal (black box). On forums some suggested ...
0
votes
1answer
116 views

Spectral density of modulated noise process

Suppose we have a noise process $F(t)$. Suppose $F$ is stationary and we know its autocorrelation function $$\rho_F(\tau) \equiv \langle F(0)F(\tau) \rangle$$ where the average is over realizations of ...
0
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3answers
2k views

How to remove heart beats interference from pectoralis major electromyogram?

I am using electromyography to detect activity on pectoralis major, however I found an interference from heart beats that is affecting my posterior analysis. The sampling rate is 2000 Hz, and the time ...
8
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2answers
5k views

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?
14
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3answers
6k views

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 ...
13
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1answer
1k views

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 ...
7
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2answers
2k views

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, ...
9
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1answer
18k views

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 ...
4
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4answers
237 views

Extract voice from magnetic tape

There is a recording which contains very noisy voice. (voice with a low Signal-to-Noise ratio). It is a female voice of a stationary speaker (right in front of the microphone) and there are many ...
3
votes
2answers
1k views

Poisson noise and curve fitting - denoise first?

If I have an image that is severely corrupted by Poisson noise, and I want to fit a function to the image, is it "better" to attempt to denoise the signal first before fitting, or should I move ...
11
votes
4answers
6k views

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 ...
7
votes
2answers
4k views

How to remove the noise without destroying the main edge?

I am working on a project. I want to segment a logo from a car and the picture's size is 3648*2432. The logo is selected by the red rectangle. I extracted this area and turn into gray level. The ...
5
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3answers
2k views

Using Total Variation Denoising to Clean Accelerometer Data

I know this is maybe a very basic question but I am doing this as a hobby and I can't find a solution to this problem. Basically I am trying to remove some noise from data I am reading from an ...
5
votes
2answers
782 views

Coherent Sampling And The Distribution Of Quantization Noise

I have a question concerning the distribution of noise in the frequency domain in case of Coherent Sampling. I read up about Coherent Sampling and understood that in order for a frequency $f_{in}$ to ...
4
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2answers
469 views

Properties of Up- and Downsampling

Given a gaussian white noise with mean 0 and $\sigma = 1$. I'm interested in the PSD (power spectral density), when the signal is plain up- or downsampled. No interpolation, no filtering nothing. ...
2
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2answers
168 views

How to detect continuous noise in audio call?

We want to detect bad audio quality in audio call. Should we extract this information from amplitude or frequency spectrum ? Is there any technique/transform/filter available for this ? Example: I ...
2
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2answers
40k views

Removing noise from audio using Fourier transform in Matlab

I'm trying to remove noise from an audio file. This audio file contains speech as well as constant pink noise. I know that I have to use the Fourier transform to convert to the frequency domain then ...
1
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3answers
604 views

Effect of noise on high and low frequency components

It is given that noise is present in the noisy image in the form of high frequency components. Can any one please explain this concept. Also please tell me that whether it is correct to say that "...
1
vote
1answer
527 views

How to compute the statistics of the DFT of correlated noise?

I would like to know how to compute the statistics of the discrete Fourier transform of a noise signal. To illustrate what I mean, I will first explain in detail a computation I have managed to do ...
11
votes
3answers
5k views

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, $...
3
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2answers
2k views

what does musical noise sound like and is there a sample clip for it?

Musical residual noise is created when a noisy signal passes through a noise reduction algorithm. For instance, please see the paper: Esch, T; Vary, P: "Efficient Musical Noise Suppression for Speech ...